Hello,
You certainly read the specifications correctly the PENDVR-ELE16C-S is a 1080p machine meaning it supports up to 2MP resolution and the PENDVR-EL16M4KX supports up to 4K resolution /8MP but has only x2 hard drive bays, although, the PENDVR-EL16M4KX offers much better compression which is h.264+ and supports up to 8TB drives for a total of 16TB which will provide longer retention time having the higher compression. The only other option would be to go with the full size 16ch the PENDVR-EL16-4MS which has 8 bays internally for drives up to 8TB each.
Please feel free to reach us via phone toll free at 866-573-8878 or via Live Chat on http://www.securitycameraking.com to discuss further.
Thanks,
Eric Wilson