I can't speak to the 5300-2 and 535, but Winix does make good products, so those are probably good units. With respect to both the Mighty and 5500-2, both have pretty reasonable running costs. Each does a bit better than the other in different areas.

The 5500-2 and Coway Mighty separate the carbon filter from the HEPA filter, which, to me, is an advantage. The 5500-2 has two different carbon filter options-one that is a carbon mesh, and the other which has actual carbon pellets (the latter being better), whereas the Coway is only the former. The Coway brand filter should be a bit cheaper than the Winix brand. Filter Monster, and other respectable third party makers, should make third party replacements for both (I've tested a Filter Monster product for a Whirlpool and found it to perform equally as good as OEM against PM2.5). Both are rated at 12 months and, if on a budget, IMHO, stretching it to ~15 should be just fine provided you are frequently cleaning the prefilter.

Probably the biggest difference between the two comes down to energy usage. To my understanding, the Coway is more energy efficient on lower fan speeds, and the Winix more efficient on higher. I feel running on higher is always a good thing (if the noise is tolerable), so if you are going to run it on a higher speed, this favors the Winix 5500-2.

One other option to mention, if on an extreme budget, is the Corsi-Rosenthal box. This is effectively a box fan taped to MERV-13 filter(s). It is not very pretty to look at, but it is very effective with respect to filtering particulate matter. That said, while its up-front cost is much lower, energy consumption is higher.