Concerning everyone who says Musharna is a better choice for offensive teams, I agree with Pocket that it's not necessarily true. I've seen more than one post saying the opposite and then listing a 0 SpA Musharna set. You need to keep in mind that Cress can opt to invest EVs into its SpA. In fact:
- Calm Musharna with a 252 HP / 4 Def / 252 SpD spread: 436 HP, 207 Def, 250 SpA, 317 SpD.
- Calm Cresselia with a 252 HP / 4 Def / 252 SpA spread: 444 HP, 277 Def, 249 SpA, 325 SpD.
Calm Cresselia with 252 SpA EVs has more bulk than Musharna both physically and specially (and especially on the physical side) and only 1 SpA stat less. Cresselia also has a superior offensive movepool thanks to access to Ice Beam and Icy Wind, which hits many things super-effectively, as well as more unpredictability because she can do so much.
If you're going to use Musharna over Cresselia, do not do so because of its higher SpA; you should do so for Telepathy and its different movepool.
You could also argue that Musharna could invest in SpA EVs to suprass even Modest 252 SpA Cresselia's SpA. However, you face competition with Reuniclus by doing so, who has even higher SpA and access to Magic Guard, enabling the use of LO without recoil. And generally, when you're abusing Telepathy, you're doing so with very powerful spread attacks that appreciate a Helping Hand boost more than a hard-hitting Psychic, so you'd probably be better off investing in bulk than SpA when using Musharna for Telepathy.