No expert on Bantams but th eone the surecharge looks most like is $50 cheaper. I'd guess knock off. Those are pouring out of Asia atm, seems like a handful a week. 50watts is popular so I'd also geuees there are components inside that will fail if pushed substantially more than 50watts. If what has caught you attention is the case and a squid multi-connector - you're paying for it, its a $100 charger selling with extras for $135.
Look at the 0610i Hyperion charger, its 250watt DC powered charger and does it all. 250watts charging power will charge a lot of battery - handles my 5S1P and 6S1P a123 pacs at 10amps -charged and balanced in about 20min.
Drop in on RCGroups.com and check the extensive battery/charger thread. If anyone knows answer to your question, it'll prob be over there. They seem to have enough posters, can find new charger reviews over there.