If it turns out you like them, then you can sell the Old Goat on the classifieds section to get most of your cost back and purchase the REO Mini.
By the same token, a Reo could be resold as well. They tend to retain their value pretty well and it's not easy to find a used one. It would get snapped up pretty quickly.
Also, for the record, the 3.7v Old Goat is MUCH smaller than a pack of cigarettes. It's built in a battery box that fits 2xAA batteries. Here's a pic of a box mod (without the feeder) built in the same box compared to the size of a quarter.
