for welding helmets, its best to try it and see if you like it. the key to a helmet is safety... is it safe and does it operate safe, you don't need to worry about much if 99% of the situations you weld in have you right in front of the workpiece. you mainly have to worry about whats comfortable to you. alot of them fit different and have different ways the helmet will fit on your head and the way you look through the lens.
autodark or non autodark is a preference as well, some people love it and some don't. it really depends on what you like. recently i've been experiencing some discomfort when doing a lot of tack type welding using auto darkening, you can end up getting little tiny flashes. so i've been using a standard lens for a bit and i find it more comfortable for a lot of welding. plus a large and wide viewing area feels a bit better, as well as a lighter weight helmet due to no auto darkening electronics weighing it down.