I think it's clear rain is gonna be strong but I'm sad Sun doesn't seem like it got many new toys. Torkoal is cool and all but not many new mons seem like they can take advantage of sun. Oh well I guess it's always been worse than rain and that'll just continue.
Rain (and Sand to an extent) have always been a cut above the other two weathers, especially hail, and they've taken a few steps to fix that in SuMo (Ninetales-A, Torkoal) but I agree it's not really enough, when Rain gets a freaking Drizzle+U-Turn 'mon with STAB Hurricane.
I wouldn't count Sun out though. Talonflame getting
nerfed BTFO is a real boon to Chlorophyll sweepers, who, really, never stopped being terrifying when given the right support. They don't get their STAB boosted, but most of them get Growth, and Solarbeam is stronger and more accurate than Hydro Pump.
Chlorophyll sweepers also got a nice teammate in Tapu Bulu; Grassy Terrain will boost their Grass STAB, and not only that, it halves Earthquake's power, providing some breathing room for your fire types. Tapu Bulu is also, in itself, a very potent wallbreaker and overall looks like a great pokemon.
Torkoal is also so much better than Ninetales. Like it's not even a contest. For the low, low price of workable special bulk and anything resembling a speed tier, you get:
-better physical bulk than Skarmory
-better utility moves like Stealth Rocks, Rapid Spin, Clear Smog, and Yawn
-better offenses and offensive movepool: Earthquake/Earth Power, Superpower, and Lava Plume to name the big ones
Something like Will-o-Wisp|Yawn / Stealth Rock / Lava Plume / Rapid Spin|[coverage of choice] is going to be much better than anything Ninetales could pull off.
Some of these will require move tutors, unless Torkoal somehow gets Drought when transferred up (it's not its hidden ability, it's its secondary ability, but in previous gens it only has one. I bet it's just a 50% to get it when transferred or something, but at any rate Ability Capsules are probably coming back.)
And to top it off, an old Sun staple, Dugtrio, also got buffed with +20 attack, making it just that much better.
EDIT: a bunch of changes also really benefit Mega Houndoom, who is
terrifying under sun but a bunch of things prevented a good team from being built around him. But now:
-It gets that sexy 115 speed on its first turn
-Sun teams can now fit in Hazard support, so Stealth rocks aren't as much of an issue
-Tapu Bulu is a great teammate; Grassy Terrain alleviates the self-harm from Solar Power and weakens Earthquake (it'll still hurt though,) and Tapu Bulu has the bulk and resists to switch in to many of the things that Houndoom fears (and vice versa a bit.)