Software is developed and changes every week, so for testing I always erase all settings before flashing new firmware. I think it's a good practice and that way always saved me time. Even if it was not necessary to erase I always do it.
LP compared to OP is now a completely different firmware. It's not only bug fixes but also new features and code optimizations. Lots of people fly development "next" branch, testing it before next release.
If it was me, I would definitly upgrade to LP, all my quads I fly "next" development branch. However, if you prefer something more stable, go for LP released version. Be aware though, that LP does not offer OP firmware, so unless you have OpenPilot installed, there will be no way of going back using LP. I also don't know where to download OpenPilot software, since their website is down.