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Upgrade. I really cannot sit and wait for apps like Adobe's and Final Cut Studio to get reinstalled, not to mention the preferences and things like that. But If I encounter problems, I don't have much of a choice I guess...

Luckily I keep most of my apps' setups on a different partition.
 
Upgrade - never had any issues with doing upgrades.

The only reason I would consider doing a wipe would be I was having unresolved problems with my system - and I don't. My MacBook has been solid from the day I bought it.
 
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