I was primarily a Castelli / Sportful guy until about a year or two ago, before starting to "collect" Rapha kit. For summer kit, I probably have 20+ bibs and 20+ tops from Castelli / Sportful (all of the higher end stuff) and about 7 or 8 full kits from Rapha.
I have not had any issues regarding Castelli / Sportful pieces, but do feel as if the Rapha stuff may last longer. Castelli is purely made for the race, and I feel like there are little concessions for anything other than to make you faster, at least in the high end stuff. Even the Rapha Pro Team stuff, which is race oriented, I feel like make some concessions for style and comfort. That said though, for me personally, the Castelli Progetto X2 pad is more comfortable than any of the Cytech pads that Rapha uses. But because I care about "style" I have begun to lean toward Rapha gear for summer kit.
Winter kit though is a different story. I feel as if Castelli and Sportful are way ahead than Rapha in innovating bad weather gear. . .the Gabbas, Sportful's Fiandre line, Castelli's Alpha jacket and whole Tempesta line. . .love them to death. I feel like that foul weather stuff just plain works better than anything from Rapha (granted I have not tried the new Shadow stuff yet). But for dry conditions, I love the Rapha Pro Team kit as well just because IMO it just looks so good.
Mind you I've gone high end stuff from Assos (style just didn't work for me, and neither did the chamois), Giordana, ALE, Santini, some Craft (still can't beat their base layers), Louis Garneau, Capo, Panache, etc. Have not had the pleasure of trying on the more boutique designer brands yet (ie MAAP), but am looking forward to doing so. And q36.5 seems like the real deal as well.
That being said, I like Castelli/Sportful gear the best for foul weather conditions. And Sportful prices from Europe a this point are ridiculously cheap if ordering from the US. Ale's gear can be found for good prices too, and even though not as technical in foul weather protection, it is nonetheless very comfortable and keeps weather out well (ie Klimatik line). I really like Ale's PRR line too, which is super comfortable. For summer kit, Castelli is still the go-to gear if you plain just want to go fast. Not quite as comfortable or stylish for me as Rapha, which is why I have Rapha kit now too. Plus kit from Panache just because I like their funky houndstooth stuff.