What is the overall consensus between the two for the Gear VR? I know that the standard S8 has a higher ppi and the S8+ has a larger battery. Are there any other outstanding differences between the two? I have heard of issues of light bleed and thermal throttling on the standard S8, can anyone confirm this?
You pretty much already have it figured out. Do you want more ppi but smaller phone for regular use or do you want a bigger phone? I have a S8+ and love it. Not sure how big the difference S8 vs S8+ in VR is.
There is no S8 light-bleed issue. I mean if you sit in a bright room, load up a dark scene, wear the Gear VR tight enough to really maximize the FOV, and then look up with your eyes (not your head) in a way that you typically normally wouldn't, then sure, you can detect some light bleed from the outside world. But in practical terms it's a non-issue. And even if it was you could fix it in 5 seconds with a self-adhesive foam strip from your local discount variety store or wherever.
I actually have some of that stuff here right now, but haven't felt the need to use any. And that should tell you all you need to know about the supposed light bleed issue.
What remains is higher PPI vs larger battery, as you've correctly determined. So, a tiny (arguably largely insignificant) reduction in subpixel visibility vs longer unaided (cordless/chargerless) VR sessions.
The standard advice, and the correct advice in my opinion, is this: choose the phone that you like best in the phone use-case context.
(also, just to anticipate a potential additional question, there is no FOV difference as both devices render a little bit beyond the physical edges of the Gear VR front opening)