Let me first say that I am 60 years old, 5 ft 9 in tall and weigh only 125 lbs. I'm a skinny geezer with very little padding on my rear. The most important thing I wanted in a new pair of shorts is a better chamois pad. I've been using a PI Attack bib short and PI Elite bib short. Lets ignore the PI Attack in this review. I'm comparing the PI Elite to the NeoPro. Both are really good training shorts designed to be snug but in no way racing tight. I've had two good rides in the NeoPros on hot humid days. My thoughts:
1. Chamois - The Chamois is bigger and better on NeoPro. They've used a denser foam that feels like a closed cell foam. It works. The PI Elite seems to have something almost as good in places but only in places. I feel like I can ride longer with the NeoPro and still be able to get on the bike the next day. I'd say for me that the PI Elite is good for about 90 min and the NeoPro is good for longer rides.
2. Weight - The NeoPro is a lighter weight material than the PI Elites. Not sure if this is a big deal but its a fact.
3. Fit - The PI Elite seems like a more complicated design with more panels. The NeoPro has less panels on purpose to eliminate seams. Seams never bothered me. The PI fits a hair snugger but remember I'm a skinny guy. I'm a size S in the PI Elite and an XS in the NeoPro. In this size the straps on the NeoPro are a little tight but ok. I wish they wouldn't size by height. The NeoPro is also cut lower in front. This allows you to breath more freely. Definitely noticeable. If you have a gut then it will probably hang out. I don't have one so this is a plus in the design for me. As for the discussion about the straps being attached more widely at the waist, I think this also helps you breath better. The straps stay in place just fine.
I generally ride about 25-30 miles at a time at about 18 mph to give you some notes for comparison. Generally I like the NeoPro but don't see any need to spend for any of the more expensive Assos bib shorts. Hope this helps
Are the Assos shorts worth the extra money? I'm keeping my NeoPros as the chamois is just too good and I like the lower cut for better breathing. Not sure? Here's where dealing with Competitive Cyclist is a plus. They allow you to buy stuff, try it out (yes that means you can go for a ride in the shorts), and return it if they don't work for you. I doubt any of the local shops carry Assos or allow me to do this.
Update May 2016
Just participated in a metric century Tour de Cure ride. The chamois in these shorts made the difference. After riding almost 4 hours, I felt fine. I doubt I could say that if I had worn my PI Elites (which I still like and use most days but for shorter rides). The minute I get on the bike it's clear that these have a denser pad which I need for long rides.