Giratina. Is it good?
Thinking of taking a Giratina to 2500CP for Ultra League
Is it worth the expense to get a Shadow Claw w/ Shadow Sneak + Dragon Claw one?
Dragon breath is absolutely amazing for pvp. Shadow claw is good, but not as good as dragon breath.
The charge moves are all kinda bad... at least they are 3-bar. Dragon claw is probably the best of those. I wouldn't waste the dust to unlock a 2nd one (unless it's one of your favorites, in which case go for it and have some fun)
Giratina is one of my favorites in the Ultra league. I coughed up the extra dust/candy to unlock a second charge move for it, so it ends up with dragon breath, dragon claw, and shadow sneak. Often, it's the Mon I'll start the match with and, in my opinion, it performs beautifully. Here's why, in my experiences:
• less-experienced players have a hard time figuring out how to counter it. Sometimes, they'll start with their Dragonite against 'Tina, but swap it out when they see how much damage they're taking from DB.
• It's very bulky, so I often don't need to use shields on it.
• Dragon Claw and Shadow Sneak act as both STAB coverage and counter coverage, punishing opposing dragons and ghosts who typically carry significantly less bulk.
• It's charge moves are on the weaker side, but are particularly spammy. This has often resulted in the opposing Mon getting KO'd after a few charge attacks get through, or they blow all their shields on Giratina, leaving them wide open for the rest of the match.
• It possesses resistances that allow it to soft-counter a lot of Mons I've commonly seen at this league (BB Charizard, HC Blastoise and company).
I'd highly recommend Giratina in the Ultra league. It really puts in work.
Mano to mano with DT/OR Dragonite, who wins?
I can't afford the dust for move #2, but my thinking is on the other side of the coin of yours, use both Ghost moves and maybe in the far future Ancient Power (since Rock has very good coverage) and field it as a Metagross counter and/or generic starting mon. I can assign my Dragonite killing to my HC+IB Blastoise
That being said, you have a very good case, gotta check the spreadsheets before deciding
UPDATE: Looks like Dragon Breath is really better, will keep mine as a dragon generalist then. Though this means I have to pay for Shadow Sneak if I want a Metagross counter
DB/DC Giratina should easily win a fight against DT/OR Dragonite. DB is the better fast move and DC puts much more pressure on the opponent's shields. Giratina ends up having much better TDO due to its stat spread as well. In the TDO spreadsheet that I have, DB/DC Giratina is #21, DT/OR Dragonite is #175.
I've had a lot of fun with mine. I caught it weather boosted so I only needed to power it up a couple times to bring it to Ultra League cap. Spent the extra to get it Shadow Sneak and it's a lot of fun to use. People I've fought didn't expect anyone to spring for a second move on it. It's massively bulky and has spammable moves to whittle down health and hopefully shields if your opponent panics.
All in all I'd recommend it.