All right, just finished the main storyline, here's what I thought.
Tepig: High
Availability: It's a starter.
Stats: Really nice attacking stats and HP, though it's a bit slow. Can go mixed nicely.
Typing: Fire+Fighting is awesome offensively, though the weaknesses to Flying, Water, Ground, and Psychic really mean it has to be careful sometimes.
Movepool: Good coverage, with its main move being an STAB Fire-type attack. Gets Flame Charge reasonably early, then later Heat Crash and gets Flamethrower just before the Elite Four. Fire Blast is also obtainable earlier than Flamethrower. Along with Rock Slide, Bulldoze, and the late-game Wild Charge, it can do damage. Its biggest weakness is needing TMs that aren't really available to stop from relying on Arm Thrust...
Major Battles: Good against Roxie's Whirlipede, Burgh, and Grimsley (minus Krookodile), and most of Team Plasma won't want to be anywhere near it either. It's also surprisingly good against Elesa. Has troubles with Skyla, Marlon, and Caitlin, though. It's also a solid backup against most anything not listed.
Additional Comments: It has slightly fewer great matchups than BW1, but I found myself relying on it more than expected.
Purrloin: Bottom
Availability: Right on Route 19, so basically the beginning
Stats: It's fast... And basically that's it. It can revenge things decently well but does nothing else notable.
Typing: Dark helps a lot against Psychic- and Ghost-types... And leaves it wide open to things like U-turn and Fighting-types instead. Not the best trade-off.
Movepool: Relying on Fake Out+Pursuit for so long is terrible. Actually, Fake Out stays the whole game. Upgrades to Snarl midgame and gets Night Slash relatively late... No real coverage, either.
Major Battles: Solid against Caitlin and Shauntal for the most part... And that's about it. Can help vs Marlon's Starmie too. It's terrible against things it lacks a type advantage against, and only can come in and really Fake Out and use a move before fainting in many cases.
Additional Comments: Almost everything I can think of is better... Best thing I can say is that it gets Cut early. That's it.
Magnemite: Top
Availability: Just before the second gym in the Virbank Complex.
Stats: Good Defense and fantastic Special Attack is awesome, and it's passable mostly everywhere else of note outside of Attack.
Typing: Electric/Steel is hardly even fair. 13 resistances more than make up for three common weaknesses and lets it beat an extremely wide variety of important Pokemon.
Movepool: It's pretty shallow, but Magnemite doesn't need much. Sonicboom is devastating and comes very early, and Thundershock is there too. Gets Magnet Bomb for a good STAB in that mid-game part where it's stuck with either Spark or Volt Switch, but then it eventually gets Charge Beam to fix that. Discharge, Thunderbolt, and Flash Cannon come relatively late. Signal Beam is an optional tutor move that isn't necessary but is still nice against Grass-types and the like.
Major Battles: Well, it has problems with Elesa, Clay, and Marshal but that's about it. It just destroys Roxie, Burgh, Skyla, Marlon, Corless, and Caitlin and is still good against the others.
Additional Comments: It basically skips the Magneton stage since it evolves in Chargestone cave, which is a nice bonus on an already amazing Pokemon.
Zubat: Mid
Availability: Caught in the Castelia Sewers at a decent level, right before a great training opportunity in Burgh's gym.
Stats: It has amazing Speed and is solid everywhere else. It's good in a pinch to pick off something weakened.
Typing: Poison/Flying is actually good defensively due to its fantastic resistances, but offensively it leaves something to be desired. That Poison type goes basically unused, though Flying is a good type.
Movepool: Has an incredibly shallow movepool, though at least Zubat comes right around the time it learns Wing Attack in this game. Once it gets Acrobatics, it just becomes a wrecking ball to anything that doesn't resist it, though sadly, it really can't hit anything that does. X-Scissor looks like good coverage but it doesn't hit anything harder than Acrobatics.
Major Battles: It handles Burgh nicely outside of Dwebble, and with Confuse Ray it can do decently against Clay. It also crushes Marshal. Sadly, Elesa wrecks it, Skyla's Skarmory is a huge problem, and Caitlin beats it. Crobat can take out something dangerous in pretty much every battle though, so despite its relatively few solo wins it's never dead weight at all.
Additional Comments: Crobat basically ends up being a Pokemon that saves wins in bad situations but doesn't create a ton of them itself, at least in the big battles. In the smaller ones, Crobat makes things quite easy.
Eevee (Vaporeon): Mid
Availability: Eevee can be caught in Castelia City, in a little park area accessed from the Castelia Sewers, just before the 3rd gym. In Vaporeon's case, Water Stones aren't available until either the Pokemon World Tournament (with 3 BP) or just afterwards when Cheren gives Surf on Route 6, when you can then get a Water Stone on Route 19. That lag between catching and evolving is quite a problem.
Stats: Once evolved, Vaporeon has good Special Attack and defensive stats to work with, letting it excel quite nicely.
Typing: Pure Water is very useful, only having troubles against other Water-types and Electrics. Later, even Dragon- and Grass-types have issues with Vaporeon. As Eevee, Normal isn't very good at all, as Eevee really doesn't hit hard enough to deal with using neutral hits.
Movepool: Somewhat shallow, but it can do. Eevee ends up using Work Up, Return, and Bite for most of its time. As Vaporeon, Surf is an incredible option. Icy Wind is a tutor move that may be worthwhile in spots, and Ice Beam is acquired late in the game and is especially useful against Iris.
Major Battles: It has trouble against Burgh, Elesa, and Clay just because it's still stuck as an Eevee. Marlon is also an issue due to Vaporeon's lackluster coverage. It's helpful if it has Icy Wind against Drayden, and is surprisingly good against Team Plasma minus Corless. It also beats half of Iris' team easily and can do some damage to that nasty Hydreigon.
Additional Comments: This would certainly be high tier if it evolved earlier, but that Eevee stage is a total pain to handle.
Gothita: Low
Availability: It comes on Route 16, which is available just before the 4th gym.
Stats: It has good Special Attack, especially once evolved, but is somewhat slow and its defenses aren't great.
Typing: Psychic is a real mixed bag. It has troubles with much of Team Plasma just because it's weak to Dark, but it dominates most Fighting-types because of that same typing.
Movepool: Getting Psyshock early is nice, but otherwise it's not too great until late. It really wants that Signal Beam tutor in Driftveil which isn't expensive, just so it can do something to Psychic- and Dark-types. Charge Beam is there too, but isn't too helpful. Thunderbolt at the Elite Four, however, is.
Major Battles: Clay is a problem for Gothita, as are Drayden and Grimsley. It's actually good for facing Marshal, but otherwise it's neutral, and Gothitelle has some trouble keeping up with neutral things late.
Additional Comments: Psychic is better than Psyshock at the end, by the way. Psychic comes by level or on Route 13, whichever comes first.
