In general mSATA is overpriced. As it is a niche market. Surprisingly Samsung SSD have the best price per GB. They are one of the best brands and the 850 Evo is one of the most renowned models. So, I'd get one of those. Anything cheaper I see is obscenely overpriced or a junk model.
Samsung 850 Evo 250GB: https://pcpartpicker.com/product/mycMnQ/samsung-internal-hard-drive-mzm5e250bw
Samsung 850 Evo 500GB: https://pcpartpicker.com/product/9hM323/samsung-internal-hard-drive-mzm5e500bw
If your laptop also accepts 2.5" SSD. I'd get one of those. You'll get a better value. There is no performance difference. Except the normal differences between different makes and models.