I personally would not buy an embroidery machine with only a 4x4 hoop. It's not a lot of space to work with unless you are only ever going to do monograms and baby bibs. I also would only get one that has a USB transfer option. I'm not sure if all the newer ones have that feature or not. A lot of them used to require cards which you'd have to purchase and get a gadget to transfer them with which to me is extra money that could be spent elsewhere...
Brother does make a nice 5x7 hooped embroidery machine that isn't very expensive in comparison to a lot of the other brands out there. If you really want one, think long about what you want it to be able to do in the end.