I have found Egos and Angels to be the easiest markers to maintain.
Read the manuals, oil and lube in the right places, change o'rings when necessary is all there is to them.
Both WDP and Planet markers are just as reliable as the other, and any marker will perform the same once setup right.
Look after any marker and you shouldnt have any problems.
When people say certain markers are crap, and keep breaking down, its usually they either take them apart not knowing what there doing, messing around with settings, or even a dead battery
I have shot both the A1 and Ego 07, both are very nice. Its all down to personal preference in how each marker feel in each individuals hands to make a decision on buying either.
No one can really make that decision for you ,but yourself.