Sidearms are fun, and can come in handy. One thing I have learned over my 2 years with airsoft, is if it aint broke don't fix it. So unless your G&G raider is having problems, dont mess with, and dont sell it unless you REALLY want something else.
Sidearms-
Any KWA series, M9s, M1911s, CZ-75, USP45, etc
WE tech- They have alot of good 1911 variants, like the old style M1911 and the Kimber Desert Warrior. WE tech is generally robust, but they just don't have the name brand backing or the warranty that covers them if you get a lemon. But they are also cheaper than KWA.
It really just depends on what you want.