Fan question

I have a 10" mdf accoustic fan its a bit too much power for my tent should i get a fan speed controller that you plug in to the mains or a variac that you wire the fan into also what is the difference between the 2 thanks

This is what I use, love it.

Its the best of both, a plug in variable transformer:

http://www.ebay.com/itm/Variable-AC-Transformer-500VA-Variac-0-130V-TDGC2-0-5-/221349838900?pt=LH_DefaultDomain_0&hash=item33897a8034