The code for Bunny Hill seems to be much better than the code for ETR. If Bunny Hill is stable, reasonably bug free, and mostly feature-complete compared to ETR, let's go with it. If not, then which would take more work: fixing Bunny Hill, or upgrading ETR to that level?
I think, you refer to the Bunny Hill code I've published on my website some months ago. The code I'm currently working on is closer to Tuxracer 0.61. The question what would take more or less work can't be generally be answered. I, for example, are absolutely incapable to upgrade ETR. Other people might shy away from the Bunny Hill code.
Probably it will be the best to wait for the Bunny Hill code. Discussion doesn't make sense without the object that's in the focus of the discussion. But I will shorten the rewrite. Some options are not substantial or important, they must wait.