I would say Hystrix only because they don't have the long tail that the retics have. I did though keep 3 retics in a 125 for nearly 2 years not that I would recommend it though.
Hystrix I would say only because I have heard they are hardier. That is if you can get your hands on one. I have been int he hunt for Hystrix for awhile now still no luck. Want to buy 2 females and a male if possible if anybody knows of any send them my way.
I understand that there are stickies to look and read but there is no need to mock when people have a question or want to discuss something. Bring some positivity to this forum and hobby, its all about helping each other out...