A few years ago, we (the family) helped my son move from São Paulo to Brasília in a convoy of my gas Hilux SW4 and a borrowed Toyota diesel 3.0 pickup (the short bed, large cab version) of the same platform. We then went offroad to play in the beautiful but rugged country around Brasília and dealt with a lot of serious mud and plenty of rocks. Both were 5sp manuals.
I did most of the driving of the diesel and all the offroad. The torque and the steadiness were assets off-road. The complaint would be that the lower top RPM on the diesel compressed the gear ranges and you had to do an awful lot of shifting compared to the gas. I hate changing gears in the mud because you can lose momentum and bog down. There was a similar problem on the rocky parts. (That area sort of goes from mud to rocks and back again. Lots of great waterfalls!)
The bottom line is you really had to look ahead and plan your gear changes. The diesel would not let you over-rev for even a millisecond, it just cut power to stay at max. That happened a lot.
The same issue applied on-road in traffic. Highway driving in Brazil is a lot of speed-up and slow-down due to lousy roads and really slow trucks passing each other with a difference of maybe 3 mph in their speeds plus maniac drivers and lax speed enforcement

. The diesel also had a lower top speed. 125 kph (78 mph) was about all it would do, and less uphill.
Performance-wise, I would stick with the gas due to range in the gears and responsiveness. The diesel won big on economy (diesel/gas differential much larger in Brazil) and maintenance/durability.
<a href="http://www.flickr.com/photos/23249464@N06/4271705789/" title="Jan05Judy´sXmasChinaItalyBahia 254 by iamthedurk, on Flickr"><img src="http://farm5.static.flickr.com/4006/4271705789_0e9e1f3cae.jpg" width="500" height="375" alt="Jan05Judy´sXmasChinaItalyBahia 254" /></a>
Here is the day I taught my son about manual hubs! He was used to the HiLux and could not get the diesel moving. I had parked on the dirt pile because it was the last spot at the trailhead. I forget the model name for that thing.
And here is a totally private waterfall (about a 3-hour hike through climax rainforest):
<a href="http://www.flickr.com/photos/23249464@N06/4271753323/" title="Jan05Judy´sXmasChinaItalyBahia 291 by iamthedurk, on Flickr"><img src="http://farm3.static.flickr.com/2690/4271753323_879a91baaa.jpg" width="500" height="375" alt="Jan05Judy´sXmasChinaItalyBahia 291" /></a>