I think you're being overly optimistic with that $20/month, but let's check...

device	analysis	financial positive ROI, ever?
HEX•FURY	https://tradeblock.com/mining/a/1849086c8c	nope, duh.  Why would you even think that's a factor when buying a Stick Miner?
Other device	https://tradeblock.com/mining/a/ec26b8d936	no?

I didn't bother with shipping costs and accessories required, e.g. powered USB hub or PC power supply
So, between two devices that are unlikely (though it's Bitcoin, stranger things have happened) to give a financial positive ROI, which would I rather have?  Heck, I'll take a HEX•FURY

Then clearly there's mad profit to be made - you should get on that right now
( no, seriously, I'd love to see more of these.  There's a gap in my list that would be filled nicely with a QUAD•FURY )