The kind of battery you select will have more weight impact than the difference in the bme zdz da 50's, they all will come in about 3.75 to 4 depending on battery, switch type, wether you use a choke servo etc, I have 2 bme 50's and they both run great. Im about to deal for a bme 44. Can you tell I really like these motors one or 2 ounces makes no difference in a 27% airplane which is about what most people use them for. I havent tached mine but 1 runs a mejlik 21-10 and the other a zinger pro 22-8 and I just put a mejlik 22-10 on it. any of these motors will give you unlimited preformance up to probably 17 lbs, very good up to 20