I cycle a moderate amount (~100km/week spread over 2-3 rides, typically in the 30-80km range), but drastically prefer starting early (generally pre-food, unless it's going to be a longer ~70km+ ride - in that case I know that I'll have to eat or I'll crash part way through). Feels far better.
I've also found that exercising in the morning, before eating, feels way better than at other times, especially in the evening.
But I've also found that my "feeling" of a session doesn't necessarily correlate with the performance. I wouldn't be surprised for other benefits to have a similar correlation.
However, as others have commented elsewhere, I think the issue for most people is not exercising at all, so for those cases the feeling you get while exercising absolutely matters. I'd say it's probably the most important thing, since if you feel like not exercising, you probably won't if it's not already ingrained in your routine.
Yes, good point - my subjective feeling of effort is often at odds with my measured performance with Strava.
And agreed on your second point too, I bike because I enjoy biking and it makes me feel better both physically and mentally. That I get good exercise out of it is a secondary benefit.
