[Amps] Variac or bucking to 200vac?

[George KB2Z]

Thanks for all the replies on loading. The amp I'm playing with has a 
200vac Japanese xform. At present I am using  12 and 24v transformers 
(230vac) in series to buck the ac mains down. I get a hair under 200vac 
(197 avg) with this arrangement. Would I be  better off using a Variac to 
buck the ac? Are there any pros and cons?
Thanks in advance, George KB2Z