I am by no means an expert in this area but I will give you what knowledge I do have via my own recruitment process.
first off, if there are 13 spots available that could be very deceiving as I have been told (depending on what the 13 actually means).
However, as far as selection is concerned it is done off of the merit list, which I have been told is a list that puts you in a order depending on many different factors, CFAT score being one of them.
as far as wait time, well I applied for Comm Resrch. It is a purple trade, so there are spots available in Air Force, Army, & Navy. When I applied back in October there was 40 spots, Dec 3rd at my interview there was 22, 2 Army 2 Navy, 2 weeks later it was 19, and It was 19 still on the 11th of January when the last update was done (at least when I had asked it was). I received my offer and it was Navy. Depending on the trade 13 spots may still be a good number. It is my understanding as well that the new numbers are released for April for the start of the new fiscal year, so if by chance the 13 spots fill up and you are not one of them, hopefully more spots will come available shortly thereafter (for instance Comms Resrch had I believe 100 at the start of the fiscal year).
I unfortunatly cannot speak on any of your trade choices, however if those recruiters are confident I would trust them, The WO I talked to way back in October had said that if all goes well I could be in as early as Feb. Which is now true. As far as wait time, Due to other things I had to due complete my application process and get merit listed, it was a period of 1 month and 20 days between Interview/CFAT/Medical and my Offer.
Best advice I can give is to utilize the CFRC they are an invaluable resource and can answer many many questions., also hold in there, the wait will be worth it.
Good Luck.