I built the Tamiya kit many moons ago and it is not too bad for its day. It had indy link tracks, which may have been a first.
I don't have the DML Grief kit, but I do have the DML Sd. Kfz. 250/5 Neu Beobachstungpanzerwagen, which I am sure shares many parts with the 250/3.
Generally speaking, the details on the Tamiya kit are a bit softer, thicker or clunkier. Also, the Tamiya kit has tools and stuff molded into the fenders, which just don't look right to me (I shaved them off, filled the holes and replaced the parts). The jerry cans on the rear are also junk.
The radios in the DML kit are beautiful and much more finely detailed than the Tamiya radios.
For my money, I'd go for the DML kit.