Any unique (or rental) BB1's are the equivalent of BB4's.
Any rental BB2's and up are equivalent of BB5's.

Why is that?
Because rental Nevada has the reload of Atlanta and the damage of Yammy, as well
as turning speed of Sima.
Rental Revenge is a little worser, mainly because of its 8 barrels, instead of 10
barrels on Nevada.
Rental Scharnhorst has a range of BB5, and rental Gneisenau can 1shot AW'ed L1
with AP shells.
Rental BB1 Ise and BB2 Fuso both have the damage of Monty, and can easily
oneshot things; Fuso has BB5's range, while Ise has "only" BB4's range.

How the hell I know all of this? Well, I came from Russian server, where we have HA
activated for almost 1.5 years, and I've driven like 6 different rental or unique as u
call them ships.

The unique BB1's are more common. You'll see the occasional unique Nevada
roaming around GB games from time to time as new fleet owners get used to it
before they need it to defend in an HA game. The Unique Nevada is effectively a
BB3, and you can tell it apart from the normal one by the 5/38 duals in the T slots
(which the regular Nevada cannot mount).

Massachusetts is a unique/rental ship, you pay like 500k for 3 uses of it(provided your
fleet holds the NY habour). It is a very powerful ship that is equivalent in power to a
BB5. You get what you pay for. I dont think I have to tell you paying 500k for 3 battles
is VERY expensive.

Sodak on the other hand is a bread and butter BB3.