I think Power Weapons should stay off Priests, unless you simply have some spare points and nothing else remotely reasonable to spend it on.
If you do run them, though, the math is actually generally in favor of the single Claw. I did the math for a WS4 Claw vs. a WS4 Power Weapon here:
http://www.dakkadakka.com/dakkaforum/posts/list/359068.page
A quick check of how things shake out with WS5 does tilt things towards the
PW, which is now better on the charge against T3 than the the
LC. With WS4, it's a push. However, with WS5,
MEQ and
TEQ have the same number of expected wounds, and the
LC is superior against T5 and up. So, ultimately it depends on your meta, which in this case I guess boils down to how often you face Xenos and Chaos, as those are the armies that most typically have T5+ models.
As for the
OP's list, I have several criticisms. First, 3 Priests is too many. You can't run one with the Vanguard squad, or they lose Heroic Intervention. I guess you could try Deep Striking a Priest near them, but not in coherency, but that seems iffy. At any rate, tooled up as they are, they should hit anything pretty hard without Furious Charge, and
FNP probably won't save them from retaliation anyway, especially since the lone Priest will not survive the enemies shooting phase.
Second, I see the SR + Furioso combo as too expensive for what it accomplishes, and taking the Drop Pod for the Furioso is very strange, since it suggests you don't plan to put anything in the Stormraven. Stormravens are meant to carry cargo into battle; as gunboats they're really overpriced and fragile. Compare them to an
IG Vendetta, which I believe is 145 points. The Vendetta has the same Armor Values, has 3
TL Lascannons, can carry a squad, and is a Fast Attack choice. The Stormraven is less capable as a shooting platform after turn 1 and costs almost 50% more.
Instead of the vehicles, why not simply load up on some more Assault Marines? Cut a Priest and the Vehicles and you could put 40 on the table.