If you're shallow like me, get the Tenn. It looks better then a glorified Nevada. And
you don't want memories of that.

Before I knew Tenn45 could mount 16s I was going to get Penn without hesitation
Now Tenn looks better to me.

Actually there is enough information to give you an idea post-ONF.

Penn43 = speed with good damage; fast no matter what engineers
Tenn45 = decent speed with better damage; fast with higher level engineers

Penn43 is a very good BB2. It can take a hit better than the NorCar (BB3) but not like a
Seva. Since it's very fast regardless of engineers, you can speed in, shoot and get out.
I don't have the Tennessee so I can't tell you anything other than what others have told
me / post here.

3x14" stink, and the Penny therefore sucks.

Any armor except bulge is pointless on any USN BB, so don't bother.

As for guns, both ships use the 14" Mk 10's pre-remodel, and diverge afterwards. The
Penn43 uses the 14" Mk 7's, while the Tenn45 can use either that or the 16" duals. Both
have the same range and per-salvo damage, though there are still a few nuances here and
there between those guns.

Also, due to a higher overheat ratio (50% versus 30%), the Penn43 can overheat much faster
at-level, plus it can use the BB III Engine, whereas the Tenn45 can only use the BB II
Engine. After that it gets muddled though, since overheat speed depends a lot on how good
your Engineers are.

if we just consider ships' data, tenny got better gun spaces and can put more amour.
penny got better engine, means you can run faster.

btw it is your choice, see if you like more speed or more amour as well as more shells