I have 2 options - I cant take both due to time contraints (family, work, etc)
1) come home and spend 1 hour on the Kurt Kinetic trainer 4 days a week
2) commute to/from work. total time 1 hour. With the possibility of a lunch time ride here and there...or extending the ride home for a little longer.
option 1 - I can push myself as hard as I need/want to. Focus on a training plan. heart rate, power etc.
option 2 - I actually get to RIDE the bike. Same saddle time, but split up and not as effective.
My gut tells me to go with option 2 - mostly because it is a lot more fun.
#2 without a doubt. Who says you can't push yourself as hard when you're in the real world? Just do sprint intervals between lights, etc. You'll have a lot more fun and feel good about yourself to boot. And the extending the ride home idea is an excellent one for more time on the bike.