Personally I don’t see much of a difference between training indoors and out, except that outdoors is a ‘less controlled’ environment. There is something to be said about riding outdoors. On a sunny warm day, it can be so awesome to ride outdoors, and with varying winds and different elevations, they can all add up to a more interesting experience, but, for people that don’t have hills around, driving there and back really sucks a lot of time. A lot of time that could be better used riding, rather than driving.
I train indoors way more than riding outside, and when I do ride outdoors, it does seem to be ‘harder’, but when I was training hard, I really noticed a huge benefit outdoors.
If you have hills nearby, I’d say do a blend: On clear days, ride outdoors, on windy dry days, ride outdoors. You do you… (Envious of people with hills)