15.0 vs 14.86 J/TH is a rounding error, so efficiency will not decide this. An honest head-to-head on the two things that will: parts and repair, and what the warranty actually covers when you buy from a reseller.

Your break-even electricity rate is hashprice divided by 24 times J/TH. A practical ASIC miner buying guide: what every spec means, real monthly power cost, hosting rates, and the total cost of ownership.