I haven't seen the Umarex MP5, but the manfacturer is Carl Walther, the same folks who make rimfire M4 for Colt. I did see a Umarex M4 and did not like it as much as the 15-22, but that's mostly because I prefer the non-Colt front sight look of the 15-22. Recall that ATI began importing the first HK clones, the GSG-5 (one of which I do have). H&K sued ATI and the settlement allowed for the sale of the stocks of the GSGs but no further manufacture or import. ATI has since come out with a GSG-522, which still looks like the H&K MP5, but must have some differences to get them by H&K. The nice thing about the ATI GSG is that any airsoft H&K accessory (and many real H&K accessories) will fit the rifle so you can jazz it up easily.