400 hps or 250 mh/hps

im lookin into buyin a used light one is a 400w hps and tha other is a 250w hps but has a brand new mh conversion bulb. tha ballast that comes with it is about 2 yrs old. should i worry about this cuz i have no idea how long they last. wat would be tha better buy??? tha 400 i 125 and tha 250 is 130 so no difference in price btw

Buy new from htgsupply.com
http://htgsupply.com/growlighttypes.asp?categoryID=1&subcategoryID=155

Buy the 400w hps light. A ballast that is 2 years old and in the hands of an unknown carrier can mean trouble in your hands. Think about it.