i strongly recommend getting an amp with a reverb option. It adds a lot more to your sound. The difference between hearing a sound without any reverb is very different to listening to a sound with reverb. In my amp, the reverb option adds a lot to the sound but if you are getting an effect processor you could leave the reverb option behind cause usually all effect processors have reverb on them. Since, I got mine.. I have been usually been playing with the reverb on my effect processors .. maybe there is a difference.
The surf guys, the real reverb hounds, generally end up not using their amp's reverb and getting a Fender Reverb tank, or a pedal, because they like the reverb to come before the preamp. Built in reverb, almost always after the preamp, is good for blues, though. I like to have reverb available in the amp, but I wouldn't let it decide which amp to get. Especially if I was considering a non-Fender amp, fewer of which have as nice a built in reverb. Or, for that matter, a smallish amp, which rarely have great reverb due to size limitations forced on the reverb tank fitting into the cabinet. A Blues Jr. is on the smallish edge of size limitation. Go for sound quality first.
