I have Econobums to use the covers over night nappies but they work really well for us during the day too, as well as Flips. They're really just the 'no frills' version of Flips. As has been said, they don't have the flaps to tuck the insert under and the poppers are in a row rather than one above the other. I actually prefer the poppers though cos if your LO is between snaps, you can do the outside snap on the right size for their legs and then skip a snap and make it a bit tighter round the waist. That's handy when you have a chunky thighed baby who has a normal size waist!
I would probably only get the outers though as I prefer the Flip stay dry inserts and they work perfectly in the Econobum outers. If you like the Flip organic inserts, you might like the Econobum inserts but they're not as soft so I'd always use a fleece liner with them. It's worth trying one though.