Big picture, I say go to UPT if there is a choice between a wait and starting immediately.
I thought I had the option to go ENJJPT while I was in ROTC (#1/6, 3.8, 99 PCSM, SP) and applied, thinking I wanted to go fighters. When I found out I didn't get it, I was pissed. Apparently, my det/cc, who was new, saw my speeding ticket I got right before packets were put in and bumped me down to #2, even though I was #1 for the last 5 semesters straight. I ended up getting Vance, and I was nervous, primarily because I figured ENJJPT was my only ticket to a guaranteed 38. I spent weeks looking at selection rates, realizing that I was probably boned and would have to go tubes.
Honestly, though, phase 1 and 2 was not that hard. If you work hard and really want a 38, you will get one, I did with really no worry. At the same time, there were people in my class that were deadset on fighters at the beginning that by the end of phase 2 had them last on their track preference. Things change, and I saw that as a good thing for 4 or 5 of the 18 AD dudes in my class.
After you go 38's, you are, for assignment purposes, exactly equal to ENJJPT - they don't get preference for fighters, it's all the same drops. I ended up gettting my fighter in the end, as did 5 other dudes in my class.
Also, you have to consider that your competition at ENJJPT is going to have almost only those motivated super cadets/people with 690 hours of flight time/real type-A dudes. I don't know if I would have been able to do as well as I did if I had been pitted up against them. At Non-ENJJPT bases, you have a mixture of people and a mixture of goals, which I realize now was beneficial to me in a competitive environment.
Waiting for a year sucks ass. While you do get a guaranteed 38, I don't think it would be worth the extra competition with respect to assignments/delay.