3 7/8" is too small. Many professionals suggest practicing on a table with only moderately tight pockets, until you develop a "professional style". Really tight pockets can change the way you shoot, and sometimes not for the better.
All in all, I recommend practicing on pockets just as tight as the tightest you will usually compete on. I plan on competing on Diamond tables at whatever majors I might attend, so whatever size my Procut Diamond Pro/Am is, is good enough for me.
I've owned it for about 2 months now, and haven't hit a ball on it!
Russ