Which iPhone 5s sold in the US is better to use in spain? Specially for LTE use
Short answer: Get the A1457 model.

You can see the different models and their verified compatibilities here. According to the site, iPhone 5s model A1457 has the support for the LTE bands which are used in most of Europe, while A1453 and A1533 have support for the most common LTE bands in the US. I don't know if the A1457 model is sold that much in the US since it supports only two US-based carriers, but if you can find it, it willl work.