Saw you at sinai. heres why-
on frumster you dont really know who you are talking to because there are no refrences and or others involved, it can get a little scary. On SYAS-there are shadchanim and they have to designate at least 4 hours a week to all the singles they have aquired. and then and only then when both sides have agreed do they talk. that is my recommendation. but i never really had mazel on SYAS so I used frumster and was B”H successful there.