From memory 8035 is V7 maps from 2014, V8 was 2015. I bought a copy back then and I can't say as I really noticed any difference (at least in the places I drive). For $299 (I've seen those maps listed for $600!) you can just about buy a new headunit with CarPlay/Android Auto support and just use Waze/Google Maps/Apple Maps etc etc. Hence why most of us are still on V8 or have upgraded their head units.

While it's very nice to have a permanent map that doesn't need a constant data feed, it's also not updated live and the RNS510 doesn't have speed camera alerts without custom firware, and even then they are silent because it's a work around at best.

I have upgraded the head unit in my Wife's Van to a Pioneer AVH-Z3100DAB, the digital part is hit and miss thanks to signal strength, but otherwise it's a great unit. I chose this because I already had a Pioneer in the car so this was an (almost) direct swap out.
AVH-Z3100DAB - Pioneer

For my MK6 Golf I'm considering the RCD330+. There is a long thread about that model here, it's the direct replacement to the RNS510 albeit with a few caveats.
Replacing RNS 510 with RCD 330+

For now though, the RNS510 with V8 maps is enough for me most of the time and when it's not I just use Waze on the iPhone screen in it's dock sitting next to the RNS.