The main advantages to electric are:
- You can race indoors
- much quieter
- much cleaner (no oily mess)
- much simpler
Probably the main advantages to Nitro are:
- You can run longer (just refil the tank and GO)
- much louder (for some this is a bonus, but not your neighbors!)
- in some ways it's cheaper (less batteries, less chargers and power supplies, etc.)
These are NOT absolute, but are pretty general.
Now, 2 battery pack will do. They will do even better if you are using NiMH packs. Nickle Metal packs don't have a "memory" like NiCads do. You can re-use them multiple times per day (just keep them fairly cool) - it's not recommended to re-use NiCads many times per day. NiMH batteries also have a bit longer run-times than NiCads do.
Get a good "Peak" charger. If you have NiMH batteries, get one that is capable of charging them. They are a bit more sensitive but chargers exist for charging them properly. There are a lot of chargers. I use a Novak Millenium Pro, it works just fine for me.