My points on each of the three:
Regice Pros:
A better Lapras, its tankiness and DPS vs double weak targets is pretty good. (Mostly in Rayquaza raids)
Potion Efficient Gyming (As long as it deals neutral or SE damage)
Cons:
Is outclassed by Articuno, not future proof at all, as Mamoswine has about the same bulk and way better DPS.
It's DPS lags behind most Ice Types.
Stuck with a one bar move in Blizzard.
Doesn't have much use outside of double weak bosses
Registeel Pros:
In the top 5 Steel attackers (Not much competition there)
Okay tankiness, but somehow less than its brothers
Cons:
Bad stats in general.
Outclassed fully by Metagross in ALL RESPECTS.
Steel type attackers typically aren't needed anywhere (Outside of Ice type bosses that don't have a Water subtype)
Regirock Pros:
Will be easier to obtain than all Rock Types, for a time.
DPS against doubly weak bosses will suffice, has more bulk than Golem and Omastar.
Most players don't have 6 Tyranitars with Rock moves
Cons:
Needs Rare Candy to fill the niche it has
Most players already have teams of Golem powered up
Community may not want to raid it, other than for dex entry
DPS is crucial, it may be too low in some cases
Tyranitar outclasses it in every respect (Except VS Bug Types, where Regirock has slightly better TDO) and it had a CD.
Those are my points. Do you agree?
Agreed, regirock's really going ot be the best of them, being someone who does have 6 CD tyranitar, I can attest to them not being up to par, its going to take a lot of time and candy to power them up, so Regirock can be a great hold over, that and with zap cannon it could be somewhat useful against
It isnt much, but it can be good
I actually wasn't aware that Registeel even made it into the top 5 for steel attackers given it's abysmal attack stat and mediocre move pool.
That aside, Regice and Regirock make for tanks against any target where they can exploit a weakness, but they all lag behind on DPS. Registeel, the robotic trash bin, however, seems to be just that - trash.
