I've always felt that it's not necessarily the memorization that matters, but the process. By the time you get to the point you can play whatever solo from memory cold, you've probably listened to it and played along a zillion times and analyzed the **** out of it. That's how it benefits you, IMO. By that time, I'd wager it's pretty well ingrained in you. And whether you can tell or not, the things that really jumped out to you from the solo will creep into your playing in various and often subtle ways. I do more basslines than solos and this is very true for me in basslines. Again, IMO.