The Brooklyn can take 5 6" triple guns. The Northampton can take 3 8" triple guns. The Northampton has the advantage in calibre, but Brooklyn has advantage in number of shells fired. I'd go with Brooklyn, but its up to you if you want more damage per shell or more shells fired at the enemy.

if this one is your first US BB decision go Brooklyn line... you can allways use your Cleveland and Baltimore as AA ships to lvl up crew... then suffer with alaska and guam but at lvl 70 you get the mighty colorado...

Northampton its a fun line but you can't use AA config on any CL/CA above atlanta and you really need to have an AA capable CA to powerlvl crew of some type (like SS)

At level brooklyn...you have enough shells so that it doesnt matter if your gunnerrs are bad( althought it doesnt hurt to have a good pair). If you have good gunners and crew, northampton line is good because the trip 8's get good spread. But the brooklyn line gets Alaska which sucks and Guam which isnt much better. The nevada is better than alaska, but overall the Alaska line is better because u get colorado (good bb2) and SoDak( good bb3) while the bb2 and bb3 of the nevada line arent that great. But in the long run, lvling to BOs so you can lvl your crew ahead of BO will help alot! Trust me, lvling a 2nd BO for both lines is really helpful. Im doing it with my UK line and its paying off believe me!

Unless you know what you're doing, Brooklyn is the only choice here.

One thing that wasn't mentioned is that the Northampton (there wasn't a space in the name of the class) has a range advantage with its 8" guns...  However the Brooklyn leads to the Cleveland which can mount a semi-decent AA battery...

Go north man, because if you ever plan to get an escort the north line is best.  but you also need to take into full consideration that the south line in the New Orleans is good for fleet battles where u can have only CA's

I'm newer player, and only to Alaska/Guam, but personally I'd go with the Brooklyn first. I've leveled a BO for both lines, and the Brooklyn line is definitely easier to use.

I really like my North Hampton, because I love the USS Louisville CA from real life. However, the ship is a lot more difficult to master, and the reload time takes forever compared to what you're use too.

The Brooklyn gets to you to Cleveland, which runs into the Baltimore. All of this ships you'll like a lot. The Cleveland an Baltimore let you provide AA coverage if you want to, and both ships pack a very nice punch.

It's also easier, IMO, to learn how to scout with the Brooklyn line. I couldn't really tell you why, but the "feel" of the ships lets me relax a bit more and scout better with my Baltimore.

Also:
1. You can AA effectively on the Brooklyn line all the way to the Montana (except the NM30). It is a very useful and effective way to grind to your Alaska/Guam in GB. Northampton line doesn't have such capability until your BB2 (Unless you have the Pensacola, which is a pay-to-have-a-better-grind option).
2. If this is your first and only BO (which is likely to be the case), your gunners are unlikely to be able to use the Northampton's intended guns at all.
3. The Brooklyn is a great CL, the Northampton is one of the worse CAs.

BUT, for your second BO and up (given that you're getting a second BO to even levels between BO and gunners/supports in BB levels, which many USN players do), you're unlikely to be able to enter Blitzkrieg (due to gunner/support level). This leaves leveling the Northampton line in a second-playthrough extremely tough as you're forced to level in GB with ships that are clearly incapable of AA, or suffer from exp penalty for your leveled crew by using low-leveled ships like the Omaha or Atlanta. (Again, buying a Pensacola solves that problem rather easily)

As far as one ship vs the other goes, NH is the best ship, it is a fully fledged CA with the range and damage of one.

However, chance are since you are probably new to the game, you will be unable to use the ship to its full potential, and yes, it requires better gunner than the brooklyn to work decently (if your gunners aren't BVE, you'll hate the spread).

Brooklyn, should everyone be good at playing their CL, would easily be the worse CL2 out there, and be a glorified DD killer and CL1 killer (then again not all of them).

But its not the case, and the brooklyn shines at making people pay dearly for their mistakes. And blitz is full of mistakes. See where I'm going? It shines.

But mostly, you'll want to ask what BB line you are taking. Both have very decent ship, and less decent one. USN BB2s are the same pretty much, with slight advantage imo to the colo vs the tenn (thats debatable tough, due to better firing arc on the tenn), but the BB1 and BB3 are not the same style at all.

Nevada and pre-BB2 tenn/penn is built for hard salvo, but with low speed. Alaska/Guam is an agile BC, that is built to pursue its target. Any non-experimented BB player with any of the two ship is going to get pwned most likely in GB. Nevada is a bit easier to use imo, due to the angles. (30 vs 45)

Now in my opinion the kicker is at the BB3. North Carolina at level has horrible spread, and is way slower than the sodak for a bit more range. The damage is noticably higher, but good luck landing a full salvo. I got both lines, and my level 120 gunners struggle to do it. The sodak continues in the Guam line of a very fast and agile pursuer, with slightly better spread and good damage. I always had a soft spot for the ship.

Another reason you should look at the BB3 first is that it is going to be a ship you'll spend a lot more time in than the CL/CA. (normally its BB2/BB3 you look at, but since BB2 are quite the same...)

So should you choose only one BB line, I'd say go brooklyn.

However, I encourage you to use the dual BO leveling (1 BB crew, 2 BB BO) that allows you to keep support at level, gunners ahead, and give you a taste of all of the BBs USN has to offer.

Also, you'll love having gunners ahead in the USN BBs. Spread at level tends to be meh.