if you pull sumo a squat suit will help,if conventional there are only two suits that i have found that make much of a difference,the old marathon d.l. suits and the new inzer max d.l. suits,adding an erector shirt with the suit may give you another 5or 10 lbs.
I have only tried two DL suits to date. Max DL which I really liked. Has to be tight as fuck though. I bust my Max DL in one of my last DL workouts and could only source a Titan Velocity in the UK. I've pulled once in it and compete in it on Sat. I will give you my final verdict on the Velocity then. lol
Everyone I know recommends the Titan Velocity or Metal King for pulling. No-one I know uses erector shirts