Should I pick a MP1, or will I just waste my time an money on it instead of playing guitar on my MP2 that have already more than I feel I really need?
Seems to me you already answered you own question.. - "more than I feel I really need"
Well, the two MP's are fairly different processors. The MP-2 has more sexy cleans, has more flexibility, more build-in features, whereas the MP-1 has it's very own distinct tone and behavior, but far less features.
Running the two in parallel, i.e. stacking up like when re-amping, into a mixer can result in a bigger, badder sound, should you want it so.
For metal, being able to stack up a clean with distortion can make things come through the mix much better than a single channel, especially if working with down tuned or multi string guitars.
Unless you feel the need for these things, it sounds to me like you're already well enough suited.
If you have a dual-channel amp of sorts, which allows running separately into each channel, you might be able to stack up the MP-2 alongside the other channel, to achieve what I just outlined above.
Another thing is that your preferred styles might benefit more from adding one of the Engl preamps, like the E530 or E570, to your rig (via a mixer of sorts - search in here for mixer ideas).
A few of those Engl's can be outfitted with a MIDI add-on that allows basic things like changing channels and such.