Are you going for looks or function? If you're worried about clanking noises, I'd say you want to look tough in the mall parking lot.
If you need something to count on during recovery operations, buy high quality non-Chinese shackles and keep them inside your Jeep along with the rest of your recovery equipment.
For the same quality shackle, the bigger diameter will have the bigger load capacity. Before you decide on the size, read how the surface your stuck on/in affects the resistance calculation for recovery operations. All of your recovery equipment needs to be rated far above the your gross vehicle weight.
If you're under thirty years of age and used to reading texts and tweets, the following may be overwhelming:
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