First things first. I'm a slingshot dealer, so take my review for what it's worth, but as a dealer, we get to ride and compare a lot of kites.
Second, I love the 2012 Rally for strapless riding and wave riding and have spent the majority of this year and some of last year riding strapless due to injury recoveries and I enjoy strapless riding.
Reason i bring this up is my twin tip riding and boosting have been few and far between. Review below is based on yesterday's session on both twin tips and strapless.
Quality, construction, etc is all top notch as always. I used the 6m 2012 and 10m 2013 Rally yesterday for training and had a guy tomahawk my kites quite often and it just kept on going.
Riding style of the 2013 is geared more towards big air, ripping upwind, tons of range and tons of power. It has a slightly heavier bar pressure than last year, but in no way is it heavy. It's slightly less than light bar pressure. Last years Rally was light bar pressure and fast turning. This year is quick turning, but jumping is insane and the hang time is better and it's more stable in gusty winds and for heavier riders.
Last years 2012 though was a wave riding dream. Fast turning that would pivot turn on it's wing tip. This years is an arc turn, which isn't as good for wave riding for some. It drifts really well though also. Both kites are similar in drift. The 2012 Rally would turn the instant you cranked the bar. The 2013 would have a very brief delay in turning, but if I cranked the bar all the way, it would turn quick, but not fast.
Yesterday was one of my better days riding in a long long time especially on twin tips. Due to many injuries and recoveries, my twin tip riding has been completely replaced by riding strapless surf boards all year and a lot last year. Plus it's fun to ride strapless.
So I wanted to try the 12m and see how it boosted. I went higher than I've ever been on 4-5 jumps on that kite. The lift is very impressive and I felt at home right away on this kite. It was one of the easier kites to feel comfortable jumping right out of the bag. The hang time is incredible, but hard for me to honestly compare to last years since i didn't jump last years much at all. I hear from others it has much better hang time.
It's going to be a hard choice between these 2 kites. Some guys, including me, like last years much better for waves, but this years for boosting. I have quite a few of last years Rally's ordered due to this knowing some will prefer that kite. It also boosts really well, but isn't quite as stable overall for bigger riders.
When I rode the 12m 2013 Rally strapless, I wanted it to pivot turn so I could make more aggressive turns. If overpowered, the 2012 Rally will pivot turn much better.
Hope this helps,