No question that the transitional year format is FAR superior to the prelim Medicine year.
Reasons why:
1) The more well-rounded experience of the trans year definately improves your breadth of knowledge and thus your performance on Step 3. (My trans year included medicine, nicu, picu, gen surg, ped surg, adult icu, gas, ccu, and ER.)
2) In a trans year, you get to know non-flea residents and attendings who you'll be working with in the OR once you start Anesthesia.
3) You're 100 times less likely to want to slit your throat/become a raging alcoholic after only a few months of Medicine (I did 6) rather than a full year's worth. This, btw, is coming from someone who went into my Medicine months with "an open mind." Only reason to keep an open mind in retrospect is that at least you won't be completely bitter from the outset, therein saving at least some of your sanity.
4) Transitional year is much more relavant to what you'll be doing later, certainly with respect to dealing with surgical disease processes, and especially if you get ICU time to cut your teeth on A-lines, central lines, and intubations. Much more useful than knowing how to write endless, worthless H&P's and soap notes.
5) You'll probably get lucky and be given a gas month in a transitional year which you'd almost certainly be denied in a Medicine year.
6) In a Medicine year you'd likely be stuck doing clinic. I had not one day of clinic in my trans year. Beautiful.
7) My non-medicine rotations were far less labor/scut intensive than my Medicine blocks were. Plus, I actually had many golden weekends, AND I got out before 9am post-call on all non-medicine blocks. Never would these minor luxuries be afforded to me on my medicine months. NEVER.
8) Medicine truly is the root of all that is putrid and evil in the world. Can I make this any more clear?
Hope you make the right choice.