I play both 3 and 4 regularly (and sometimes also 2). I played TS3 years back when it first came out, but after a while it developed graphics issues that made it totally unplayable on my Mac. Then TS4 came out and I switched to that. But around 2020 they released a 64 bit version of TS3 for the Mac and I was really excited to get back into it again. Since then I've gradually caught up with the packs and Store worlds I never had before. I still have to be careful when I play as it can crash very easily, and I wouldn't play without the core NRAAs mods which stop some issues becoming more serious. But I'm having great fun with it.
I have to say though that I do prefer TS4. Partly because I first discovered the Sims with TS2, and 4 is more like 2, and also because I just prefer the look, the art style and the graphics of 4. Some people don't like the shell buildings in TS4, but I love how full the worlds look (even if most buildings are empty) and how the Sims themselves look. For me, I think that playing both games alongside each other helps me appreciate each one more.