First off are you 2wd or 4wd? Second is are you leveled? If you are 4wd and leveled then either spacer will work for you but be sure not to try and save money if you are going to buy them. I had 1.5" on mine and took them off for the winter just so I wouldnt sling salt all over the side of my truck. The look is good but there was always that looming though in my head that one would fail and I would lose a wheel. Just my .02
2006 King Ranch 4x4, Rancho QL, Camo Tan Plastidip Trim, Straight Piped, SCT x4 7015 Tuner, LED Headlights, 20x9 Mamba M2X Wheels, 295/60/20 Nitto Terra Grapplers.
I personally would never recommend using spacers. But if it's really a "must", go with whatever floats your boat more. As far as which "would look better", it depends on what wheel you have currently, the offset of the wheel and 2wd or 4wd as mentioned (KCCO by the way) above. Without more information, your question is way to generic.
From my personal experience I wouldn't run wheel spacers. I just had my pair shear the studs off. But if you are gonna do it anyway I wouldn't go more them 1.5 and get a good pair not a pair off eBay. Make sure to check and torque them down regularly
04 F150, 2.5 HBS leveling kit, 295/70r18 terra graps, flowmaster super 10 SIDO exit in front rear passenger tire, bedlined bumpers and rockers