depends on your experience and the quality of your horse. i started unaffiliated with welsh boy coz i thought affiliated was for pro's. i worked up to elem unaff before finally giving aff a go after a lot of pressure from my instructor. didn't think i'd be good enough, but got points and placings on 1st outing and clocked up 81 points, 3 trips to the regionals, 2 top 6 placings at the area festivals and 4th at the winter champs in the next couple of years. if doing it again from the start i'd probably just go for affiliated, but the points clock up quick so i'd make sure i was established at home first. if introducing a baby to dressage, i'd go unaff first just to get it used to going out, then go aff prelim where you dont get any points. the judging is much more reliable aff, but obviously it costs more money (£100 a yr plus more expensive entry fees) and you clock up points and put yourself out of a level. good points are better judges, prestigious finals to qualify for, chance to be in H&H, better competition etc