I sure as hell can't do 1:47's @ Thunderhill which is what the best can achieve on a 600. Hell, my rd roll's along nicely and I'm right near 2:15's even with suspensions issues. I'm just thinking how nice it would be with something plush. I've got way to much off throttle chatter that's quite unnerving. I have quite a few years of track experience under my belt, even if it was 30 some odd years ago. And I've kept kept my wife 37 some odd years and you would not want to meet her sister.
Would love to help you with that chatter problem...
Back to the question, it really depends on how you think you want to ride this potential new track bike. For me:
250 Pro - I love the 250, lots of fun riding at the upper limit all the time and even more so when there is a group riding together. You can do a season on 1 or 2 sets of tires for the schedule you were thinking. (I personally got 9 track days out of a set and they still looked great, but too many heat cycles)
250 Con - You will get passed in every straight and it requires a good amount of concentration and diligence to keep speed and out of peoples way as you go back around them in corners. Lots of shifting.
600 Pro - Lots of fun and will feed the adrenaline craving. Well sorted, they handle better than an RD albeit heavier. However, can be ridden fairly effectively using only 2 or 3 gears.
600 Con - Can be hard on tires if you are not mindful of air pressure and suspension setup. Will typically lose the drag race with the liter bikes. R6 has a racing seating position.
1000 Pro - Lots of power. Can be ridden at a fairly good pace only using 1 or 2 gears. Seating postions are usually a little more relaxed than their 600 counter parts.
1000 Con - Weight, fuel.
I personally am pretty easy on tires 900+ miles on a set of Pirelli SC2's before replacing them and could have gotten another weekend out of them had the last day been at Sears instead of Thill. I would imagine the same distance on a liter bike as well. But I am pretty light on the throttle and just try to carry corner speed on exit so I don't have to twist the grip quite so hard down the straight.
This year I have logged some miles on my FZ-09 which is completely different than the race bikes, but reminds me of my days on my 81 Seca 550. Very accommodating seating position but can still get some business done when needed.
So how do you want to ride your 2015 season? Like a race pace, spirited track pace, peppy street pace, or just lettin you all know I am here pace?
There's a lot more I could type, but can't at the moment. :teeth