US DB are clearly better than TB.
US t2 TB are big and slow with average damage.

DBs will naturally dominate the blitz rooms. TBers on the other hand are late bloomers,
you won't get much from them until they become AAW immune. A special note though, US TBs
have the second highest torp damage (the no.1 being UK TBs).

However, I have seen a cv can manage two types of bombers at once (or with another CV) so
why not both if you can?

actually DBs or TBs it dost matter. but the important thing is how u manage ur soldier
positions.. low level soldier will has many exp if there re bording high level ship or
train with high level soldier..

dbs give more exp i heard mixing lowers exp gain like gun and torp use in blitz but i recommend either all db or all tb

Me personally I go with an extra DB.