Having done West Africa for 5 months in a 90 300Tdi, I would say that it is very good for the job, as long as you sort out a good storage system - the 110 is a better overland vehicle as it is easier to fit 2 or 3 fuel tanks a large water tank and generally carry a greater load of spares and equipment. The Guys are spot on with the Hardtop/Station wagon comparisons - the Hardtop for 2 people is unbeatable and really works well, the station wagon is a much more usable vehicle for more than 2 people and after you have finished your trip.
For me the 90 is still the perfect overlander - with a roof tent - in the Sahara I could drive anywhere I wanted and run rings around overweight 110's and Landcruisers - with the 110 you fill the space available and before you know it its full to the roof and access for things becomes difficult - which ever vehicle you use pack light - use good quality lightweight gear and take enough to be comfortable -if something doesnt have at least 2 uses leave it at home.
The 300Tdi is a great engine, in the 90 it has the perfect combination of power and economy, in a heavy loaded 110 in soft sand it is a little underpowered but acceptable - the low range makes up for this to a certain extent, and for travel in Sahel conditions it has enough power - and fuel economy that Land Cruisers can only dream of...
25000 km I averaged 28 mpg
Best 32.5 mpg on sealed roads in Mauritania with the wind behind !
Worst 24 mpg in hot soft Sahara sand
thats pretty good.....but its beceause I kept the weight down....
Having driven the 130 Extensively off road in all conditions I would avoid it, the Ramp break over angle is not good for Sahara Travel and it is even easier to carry too much gear it - when loaded the 300Tdi is not powerful enough to give it good cross country ability, you need to be looking at a 4 litre + turbocharged 6 cylinder diesel - nissan or mazda conversion.
if you need any more info no problem, Cheers Grif
Ex Dragoman/Encounter Driver, Land Rover/DR650 Overlander

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Cheers
Grif

'11 KTM 450 EXC
'09 Suzuki DR650
'00 Discovery Series 2 V8
'95 Defender 90 300 Tdi Overlander
http://gipperstravels.blogspot.ca