First of all composing tunes with V4 is several times quicker than on OSS as the UI is much simpler, logical and simply working. Secondly, because of the things mentioned it is also easier for beginner to learn. This of course the case only if the user wants to create 4ch/8ch-tunes with Paula. If the user is going to use MIDI then I'd advice to start on OSS aswell.
I remember I tried OSS several times when it came out, always returning to V4 as the "new look" was soooo confusing. It still is, I did a remake of Lost Patrol yesterday and was cursing the userinterface half the time ;-)
Grab it here:
Lost Patrol remakeps.Its been two years since I last touched my synth and OSS.. so please forgive me its crappiness