Another vote for ABL3.
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THX to this thread I went for Phoscyon 2. 
I like its UI better than that of ABL3. No technical or soundwise decision.
Expensive? YES! However luckily ultra intuitive UI and its fun. Comfortable and very easy to get a variety of decent results in comparison to my TD-3 and its several editor tools.
I don’t know whether it is the “best” 303 plugin, I don’t care to be honest.