I personally own both, a 3500 Aisin and a 2500 68rfe. There is NO comparison which one actually feels like a true heavy duty transmission. The 68rfe shifts way too soon, it will have the motor lugging around 8-900 rpm at which point the governor on the motor causes the truck to "surge". Putting it in tow/haul mode helps, but even then it shifts WAY TOO SOON. When I'm pulling 7,000lbs, I don't want the dang motor at 1,000 rpm! LOL The 68rfe also will slam into gear now and then, it seems to get confused easily if you are in a situation where you really step on it, then let off cuz some idiot cut you off, and then step on it again. The Aisin is ALWAYS in the right gear, shifts firm but not harsh in the slightest, doesn't have the "flare" you may have seen others complain about, actually will keep the rpm's higher when in tow/haul mode, and it allows the exhaust brake to work MUCH better.
In the 3500, I actually feel like I'm driving a true Heavy Duty pickup. The 2500 feels like just another truck. Don't get me wrong, I really like the 2500 and how it rides, and it is quicker than my 3500 even though it has less hp and tq (I'm sure because it's lighter) but if I could have had the Aisin in the 2500, I would have gladly paid several thousand more for it, it really is that much better of a transmission. I agree with TC, personally I won't tow anything super heavy behind the 68rfe, it handles my 6k boat like it's not even there but the other day I had to move a 12k roller across town and used the 2500 cuz the 3500 was already under my gooseneck, probably the last time I will tow that much weight with it, it just didn't feel comfortable. (I know, I know, there are plenty of people here that tow huge weight with their 68rfe's and love it, however I feel if they drove an Aisin with the exact same load it would be a different story) I had a 2010 3500drw with that transmission that I would hitch up to a 24k trailer for a total gross of 33,000lbs and it was HORRIBLE! So bad in fact that on my first trip towing out to Seattle, I stopped at Dave Smith and ordered my GMC Duramax / Allison on the way home.
On a side note: The reason I didn't just buy a 3500 srw was the coil spring suspension on the 2500, I am ordering a complete airbag setup to try and get the best possible ride since this isn't my only truck.
If I was in a position where I could only have one pickup, it would be a 3500 srw hands down no question about it. With the transmission being probably 75% of the reason for the decision.
:edit I really think you owe it to yourself to drive both, actually put a few miles on them, not just around the block. Any dealer worth a cr*p will gladly let you drive them. Even if the Aisin isn't equipped the way your want, at least drive a truck with the transmission in it. I think that will probably make your mind up for you.
