Oh it's easy to do, especially since both of them are usually towards the bottom of the server select list (normally AB is Full and LDL is Heavy). I have characters on both and I rarely experience any horrible lag.
A few notes:
* Not everyone RPs. There are some people who do, but most folks who do keep the RP in groups. I'm kind of new to AB right now, but I know in Freeport in LDL there were complaints about a lack of RP from some people (there are people trying to get stuff together though).
* You will still run into idiots. Both servers have come to a general policy of /petition'ing any name that isn't condusive to roleplaying. While this can turn a lot of people off to the server, I understand the general point, it sucks to be getting involved in a game only to see someone like Purrrrrrrrrrrfect run past you (BTW, Purrrrrrrrrrfect was a Kerra :P :P).
* I have found a lot of folks helpful (haven't played on the other servers really so I can't tell you how they compare).
Hope this helps you in your decision to play on one or not.