Man... I just wrote a reply, and after checking back on it I realized that it doesn't answer your question AT ALL!
Huzzah for reading comprehension.
But fuck it, I'm going to post it anyway, cause I'm interested in how you fine folks feel about this:
Aside from the buffer delay issue, I must say that I personally prefer to practice on a small amp over even the greatest amp sims.
The thing with practicing on amp sims that bothers me is that they don't sound like an amp and a speaker in my room; they sound like an amp and a speaker in a room, through a microphone, through a speaker in my room. For recording purposes that's fantastic, but for playing by myself, that just feels like something's missing.
Compare it to drawing an image and afterwards cropping it to contain the best possible view, before putting it in a nice frame. That's cool, but I would hate to draw in the frame from the start. I just wouldn't feel it that way.
So yes, IMO get a small amp setup to practice on, but find something you vibe with. It doesn't have to sound like a million bucks, as long as it keeps you coming back.
For reference: my big setup is mainly a 6505 through an Engl 4x12 V30 with a GT-10 for FX.
My practice setup is a RAT through a Box of Rock, through a simple delay pedal, into the FX return of a TSA15 combo (any other clean amp of the desired volume level would work).
I really enjoy that practice setup and its versatility so much that just looking at it right now makes me want to play. Anything that does that is a winner in my book. Maybe it's not the case for others, but I've personally never had that feeling towards an amp sim.