The question is really difficult. Let's exclude the passenger tires from the consideration, for understandable reasons. LT265/75 are taller than LT265/70 about 0.7" (30.8 vs 31.5). Taking into account that this is DIAMETER, not RADIUS, the 75s probably will give to you about 0.3-0.4" of additional vehicle height. Not much, but on a trail, every millimeter counts. You can offset it by additional coil spacers and more trosion bars crank.

75s advantages:

- vehicle is taller;
- tires roll over obstacles easier;
- tires are stronger;

70s advantages:

- you do not need to cut fenders;
- crawl ratio and speedo are less affected;
- softer ride;
- tires are lighter;

choose what is more important for you ...

Best regards,
Oleg