The Altronix RB610 appears to have screw-terminals for the control inputs whereas the eBay module uses square-pins that can be a nuisance to deal with. Of course at $4-5 per relay (vs. about $1 per eBay relay) you can buy a lot of screw-terminal blocks or other wiring accessories with the money you "save" on the relay cost.
What's also curious is you can order the RB610 from Office Depot of all places!