Funnily enough, while v510
does fix some bugs that v500 had, it also holds bugs the prior version didn't have. Like first off, in v510, you're not allowed to delete every vanilla map and create new ones. That can actually crash and corrupt the executable file. And that bug HAS been reported to Leo40Story when it was in development a full year before it became an official update by Noxid. No fixes were made at all. While I understand that performing an action like this is a more advanced technique if you wish to optimize your mod or to just start completely from scratch, neither earlier version of Booster's Lab or even Cave Editor would corrupt your game and make it unreadable through performing that action.
There is also an incompatibility issue within v510 if you're using Windows 7 (take this with a grain of salt, as it shouldn't be an issue now considering W7 is now made obsolete by Microsoft), and you decide to look at the built in tutorial guides, they will not be read due to an "error" in how the files are being read. This issue was reported to Noxid not once, but
twice, no bugfixes were done.
If you care about the basic functions (map editors, TSC editor, Hackinator, CSE2 modding), v500 and v510 are identical to each other. If you wanna mod CS+ and CSE2, then v510 is definitely your best option. If you'd just rather double click instead of pressing the i key for dropping entities into the map editor, for memes and nostalgia's sakes, definitely go for v430. If you wanna smoke weed every day, go for v420. But when it comes to which version is the most stable one to use, I'd definitely recommend v500 over v510.