You buy what you like. I was holding one of the MP5SD models and had a peice break off in my hand. I looked at the STG44 model and from through the mag well I saw what looked like either the bolt or some part of the receiver that looked like the cheapest metal in the world.
I would touch anything they make and would put my money into a proven 10/22 or one of the CMMG type M4 styled .22s
Personally for me, I am looking at a CZ bolt gun, mag fed, bull barrel in 17HMR, Squirrels will fear me