Hi,

Okay, so I am not a trainer, and maybe some people with more long-distance experience could better answer this - BUT for what it is worth, I do think they are very compatible - maybe even both necessary together - because I imagine that training long and training hard complement each other. Here's a sample training week DURING TRAINING SEASON from my coach:

Monday-Recover (30minutes-1hour)
Tuesday-Invervals (1-1.5hours)
Wednesday-Intervals or Aerobic (1-1.5hours)
Thursday-Aerobic (2hours) or Intervals 1-1.5hours)
Friday-Recover (30minutes-1hour)
Saturday-RACE or Long Hard Ride (2-6hours)
Sunday-RACE or Long Aerobic Ride (2-6hours)

So basically, this plan tells me that I am both building base and distance while training for strength and speed.

In the winter - almost all rides are aerobic - and longer.

I have been out ridden by women who do not ride fast but are just so darn fit can keep going and going. I poop out in long rides, but when I first started riding, working on speed helped my comfort level and speed in centuries. My first century took 8.5 hours (flat) then I was able to do a century in 5 hours and 20 minutes (flat, too) - and that was while I was training for speed.

Again, I don't want to make a recommendation, but if I were just starting out, I might do one interval day during the week, one fast group ride on the weekend (even if it's longer) and then ride long on Sunday, rest Monday and Friday, and do medium aerobic rides Wednesday and Thursday. If you are new to intervals and such, it's good to give your body a chance to adjust and to avoid overtraining - even the one session a week will help.