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I have both on this machine. They do interact - it seems that if you do the default install, preferences and caches are shared. For initial set-up the sharing of preferences is actually a convenience - you only have to do the set-up once, and it works for both.
I intend to go change the default directories in both to see if I can disentangle them, but in the meantime, they both work OK. You cannot run them at the same time using the same username, but again, I believe this is because of the preferences being shared.
Jim