What do you guys think will be more economical in the long run?

Getting an old 4x4 SUV/AUV in gasoline and convert it into LPG, or get an old diesel SUV of the same model?

example:

Pajero gas/lpg vs. diesel
Trooper gas/lpg vs. diesel
Terrano gas/lpg vs. diesel
Patrol gas/lpg vs. diesel
Adventure gas/lpg vs. diesel
Revo gas/lpg vs. diesel

Kasi I noticed that these types of vehicles tend to consume a lot of gasoline. Sometimes their diesel counterparts are more efficient liter by liter. Of course lpg is cheaper than diesel, and maintenance wise, masOK ang LPG. I am looking at the vehicle for possible better resistance sa floods, in which case baka masOK ang diesel, pero kung mataas naman talaga yung sasakyan, I think the gas/lpg cars will manage just as well. What do you guys advice?