The good news is that no matter what you pick from these choices you will have a great engine. personally I dont like the manual advance linkage on the brison. I like bme's so much I just picked up a 3rd, a lightly used bme 44 to go on a pitts special my 50's run like swiss watches. The DA seems a bit pricey to me. If you dont mind high octane gas ( only a pain to use if you have other gasseres that dont need it therefore requiring 2 different cans of gas) and you are buying new that zdz 50 looks attractive for the price. If you like the conventional beam mount the bme is the way to go. Just my opinion--- and Im likely to change it by tomorrow....