Hey Jimbob, welcome to Singapore in advance. I have never tried the rest that you named, but Portia is rather well-known. She and Primaleen probably belong to the "legends" category, while the rest are all... average I guess? But I suppose it's all up to an individual's taste.
Primaleen is a sure bet. Can't go wrong with her. Pretty, feminine, sweet, kind and tonnes of fun. Rock hard where it needs to be too!
As for the price, it's gonna be hard for you, since you're a tourist and they usually hit tourists for more. See if you're able to pass yourself of as a local or at least a long-term expat here. Go for 150, or even 100 on a weekday, if you manage to pass off your "disguise". If not, be prepared for maybe 200? IMO, do NOT pay more than that though.
Otherwise, if you want to be really cautious, just go to Orchard Tower and take your pick. You get to see and feel instead of taking a random stab on the internet. In fact, if we happen to be going too, you could come along and get an orientation tour :P
Have a great time, post again if you need help!