Touching your own dick feels great, but after so many years of doing it you're not likely to discover anything new or different there.
Touching someone else's dick is great because you're getting to explore something new that is like yours in some ways and yet not like yours in others.
Dildos are quite literally a tool designed to do a job, and touching them isn't particularly enjoyable. I'm curious to see how much like a real dick one of the new "ultra-realistic, dual-density" dildos feels, but even with those I seriously doubt anyone is going to mistake one for a real dick.