I know it's been done to death, but here's my comparison over a 2 year progression of distance riding, for 5 pairs of bibs (4 shorts, 1 winter tights).
When I started getting back into riding, 40mi was my "long distance" ride. My average week was 60 miles on a 15 mile r/t commute over mostly flat terrain, on a rigid MTB with 1.75" street tires. I'd ride the occassional 30 or 40 miler, and even did a few 50 mile days.
I bought a pair of Performance Century Gel bibs, because I didn't know any better. They're heavy and have low-compression fabric; but for a beginner's behind, they're comfortable on a 10 - 20 mile ride. Once I started riding longer distances, I realized that maybe they weren't the best shorts out there. Eventually, I upgraded my bike to a new 'crosser outfitted for road riding, and worked myself up to doing a century. Although they're called "Century Gel" bibs, it was that first century ride that sealed the deal: I needed new shorts... The Century Gels were too hot (gel padding isn't breathable) and caused too much soft tissue pressure after a few hours in the saddle.
I decided to try a pair of Performance Ultras. They were on sale, and FWIW, the Century Gels didn't fall apart on me, they were just not comfortable for the type of riding I was doing; so Performace was an OK choice in cost-effective brands. The Ultras are nice: They're a higher compression fabric, thinner and better wicking, nicer leg grippers and a mesh upper to keep you cool. The padding is a split center mid-density foam with a microfiber cover so it's smooth, breathable and very comfortable even in the heat. I put over 4000 miles on these shorts. The seams showed a little abrasion pilling at the inside of the thighs, but I ride a laced Brooks saddle so this didn't surprise me. The fabric never wore through, and the seams never came apart. I rode over a dozen centuries, a few double metrics, and a double imperial in these shorts before wearing them out... but they are worn out now. Although the fabric is fine, the padding has fallen flat. It's no longer supportive, and just squishes down as thin as paper underneath me.
Overall rating: 3.75 of 5 Good shorts, comfortable for a big guy like me, but they could have lasted another season, IMO. Would have been a 4.25 of 5 if I got a second season out of them.
For the cold and rainy months I wear Pearl Izumi Gavia Plus bib tights. OK, first off, they're expensive. On sale I paid almost $200 for them, but they're worth every cent. They're a good fit in the 2XL, which is nice that PI understands how to tailor a cycling garment for us fuller-figured cyclists. For being a wind/water resistant garment (typically means less stretchy) there are no binding or cinching feeling areas. The legs are cut reasonably wide (I have 28.5" quads and 17.5" calves) and even the length is good (I'm 6'6", and typically have fit issues with length.) The only complaint I have is that it could be a little longer in the torso. It's comfortable on the bike, when leaned over in a rider's crouch, but standing up you'll feel it in your shoulders. The padding is PI's Thermalfleece 3D-PRO, which is different than their summer weight 3D pads if you're familiar. It's a slightly less breathable pad so you don't freeze your privates in the winter cold. It's thicker and more firm than the 3D Elite, with a microfleece covering that (if you use any) tends to 'soak up' chamois cream so you have to use more of it than usual on the first application before a ride. The fabric has held up phenominally well, the padding hasn't collapsed even after 4 centuries, a double metric and a 300k (which gave them a 17h punishment test.) The ankle zips are secure and problem free, and the seams have all stayed intact.
Overall rating 4.5 of 5; half point loss for being short in the torso.
I can give the following 2 pairs fit ratings only, based on yesterday's brief test. Castelli's Endurance bibs and Pearl Izumi's Slice Microsensor bibs.
I know that Castelli has their advertising slogans "designed to hang funny" and "display in attack position only", so I'm aware that they tailor their garmets for fit while on the bike. The Endurance bib is no exception, and they were more comfortable when leaned over in a riding crouch: The shoulder straps felt better, the front didn't "pull" as much, the rear end felt snug and the padding settled into the proper place. However, even a 2XL wasn't cut right for a guy my size. These things are short... I mean, like hotpants short. I'm not sure if they're standard 9" inseam or not, because they were riding well above my tan line (from last summer, still!) on my quads. The other issue was across the belly; they were a little on the tight side for my preference. So I decided to give the PI's a try.
The PI Slice MicroSensor bibs were much better, and it could be because they're a "performance recreation" short rather than Castelli's race design. They're longer in the shoulder with a wider strap and larger coverage on the upper half, but it's mesh so it won't be hot in the summer. The length of the inseam is much better than the Castelli shorts. The PIs have a 9.5" inseam so it even ran a little longer than the Performance Ultras. The padding is a comfy (3D Elite) without being bulky feeling, even off the bike. The fit seems much better suited to the slightly more upright, bars even with the saddle type of riding that I do, opposed to the Castellis which only felt proper when I was crouched over like I was in the drops. The Slice Microsensors are amply cut across the midsection while still providing reasonable compression on the rest of the garment, and the microsensor fabric feels light but sturdy.
I had initially gone into the shop to find a pair of Assos Uno Logos, but the shop didn't have any, and these were the next two suggestions in a similar price and performance range. (~ 130 - 150 bucks, distance recreation, training).
Long story short: If you're just getting started, Century Gels from Performance are OK, but I don't suggest them if you plan on riding more than 20 - 25 miles at a time. Performance Ultras are a nice step up, and make a great pair of distance shorts... but be prepared to replace them every season. Pearl Izumi knows how to cut a garment for us bigger riders, and I've had good luck with their tights so now I'm going to torture test a pair of their shorts. Castellis, while very nice, didn't seem to be cut well for a big dude, even in their 2XL size.