I would quarantine first then delete later if everything is ok. When removing spyware and parasites, on occasion their removal can cause something to not work right. If you quarantine, it cannot run, but it can get restored to get the PC working again if needed. Also sometimes you may delete something that later you decide you wish you had not removed.
I've heard of viruses infecting a system file like Explorer.exe and the anti-virus software detected the infection but instead of fixing the problem, deleted Explorer.exe. That's just one example. Quarantine is the safest way to remove malware. If your PC and your programs are running correctly after a period of time (say, three weeks), then you can clean out the quarantine files.
-Don
<MOD Edit>
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