theres a few more differences than that. 26cc motor vs 23cc, their "tuned" pipe, heavy duty shocks, etc.
taken from ddm's website on the 5bss kit description
The HPI Baja 5b SS Kits are now available. The item is a KIT and requires assembly. Key upgrades from the regular HPI Baja 5b include 26cc "Fuelie" engine, heavy-duty shock set, modified rear shock tower brace, aluminum tuned pipe, heavy-duty rear dog bones, heavy-duty beadlocks, aluminum alloy differential case, clear body, metal gear steering servo, gunmetal chassis, orange anodized aluminum parts, heavy-duty shock set with thicker shafts, front and rear sway bars, 8000 RPM clutch spring, and more. Radio/Receiver, throttle servo, and receiver battery not included. HPI part # 10610
and if your wanting an upgraded motor out of the gate you can get the kit without motor and free dominator for 700 bux.
it all depends on how much time you want to put into playing with it to start with. you will need to get rx/tx, throttle servo and battery as well as the kit.
me personally, the next one i buy will be the ss kit form of whichever i get. i have fun building them and you learn a lot about them while assembling them. makes repairs later easier as you've already put the pieces together, so you know where to start.
my $.02
