Of course it depends on how much you are willing to spend. New, or Used. Warranty or no warranty.
I like USED. Mine have no warranty. I buy Ford F250 or F350 7.3L Powerstroke in either the Old Body Style (OBS)1994.5 - 1997, or the SuperDuty 1999-early 2003. We have 3: 1996 F250 4WD (170Kmiles), a 1997 F250 4WD (230Kmiles) both extended cabs; and a 2000 crew cab Lariat 4WD DRW(130Kmiles). This is the one we'll use for the longer tow-trips. We like the long beds. We've put 20K miles on the 96, and 120K on the 97. Replaced one transmission and had exhaust work done on the 97. Bought the 2000 and had to do the turbo, exhaust up-pipe maintenance, door locks...
The 3.55 is a good way to go since you will not be towing all the time. It gets you better mileage, less wear and tear (70-75mph at 2K rpm) vs the 4.10 (at 2.5k rpm?). Our older trucks are 3.55's and they pull the Liberator, or loaded 3-horse-trailer no problem. The 2000 has the 4.10.

If you can find someone who has maintained it like you do, you can get a reliable SuperDuty, with 100Kmiles-130Kmiles, for about $17k-24k. Even less for the OBS. The lower mile Super Duty trucks, with around 100Kmiles, can cost $26K. You have to determine if the normal issues are taken care of - transmission is good or replaced after 150k miles ($1K-1.5K), the turbo is not dusted ($1K-$1.5K)...the exhaust system in good condition...the door locks work, etc.
If you get a 2003-2007 6.0L from someone who has sorted it out, you can get a pretty nice truck with lower miles, but I prefer the 7.3L.
2008-2010 6.4L, maybe better than the 6.0L overall? Not so sure about the fuel mileage of the 6.0: and 6.4L they are probably less than the 7.3L fuel mileage.
If you want to spend around $30-35k, you could get a 2011 F350 crewcab Lariat 4WD DRW or SRW for 6.7L with a warranty. I think this is what I'd get next - if and when I replaced one of the others. I just can't see buying a new one for $60K plus tax, license, higher insurance (and finance charges!).
That's my experience - never driven the other Diesels - never felt the need cause I find the "old" Fords gave me all I needed. I'm sure others can tell you the pro's and cons about them.