The are few basic differences between 1/8 and 1/5:
- Money: 1/5 is way more expensive
- Weight: 1/5 is much heavier
- Lipo's: 1/5 needs a lot of high quality lipo's
- Handling: 1/8 handles better and is much more suited for jumps and i.e. backflips
That said (i own both 1/8 and 1/5 on 6s and...