I'd be inclined to claim that eMac is the really reasonably priced alternative, bang / buck. You can find those even cheaper than Efika.
As an Efika and Mac mini user I must admit that the eMac and in particular the Mac mini are the much much more versatile devices. The efika actually *can* deliver much fun, but more for tinkering projects, low wattage setups and for the sake of it. It is a nice device and it is pretty useable for many things, but then again the RAM limitation is a bit annoying (well, it is okay) as is the limited cpu power (also okay for a lot of things) the not too fast ide interface and usb 1.1.
The Mac mini G4 and MorphOS are really a dream team (nonetheless I really ike my Efika and use it a lot, too).
If your funds are not too tight I'd go for a Mac mini, if your budget is rather limited an eMac is a pretty nice option.
