1) 3M - cannot filter bacteria, and amount of carbon block very little, contaminants reduction definitely not as good as those with 2 - 3 carbon block cartridges. I cut open 3M AP Easy complete before and the media inside is much smaller, compared to the size of the cartridge.

2) Panasonic with 0.1 micron, can filter bacteria but using granular carbon not carbon block and since it is a 3 in 1 filter, amount of carbon and membrane will be very little, high chances of clogging for area with dirty water supply and do not have an outdoor filter. Ability to filter VOCs, chlorine and etc might not last for 1 year but we wont be able to know.

3) Coway - only membrane no carbon, membrane is not really effective in filtering contaminants like VOCs and chlorine as suggested online, even RO filters with 0.0001 micron also need carbon filter.

These 3 models have their own pros and cons. Since budget is limited, if you let me choose i will get panasonic.

NSF : http://www.nsf.org/
they certifies millions of products

out of those 3
do a comparison of the below :
do check out the list of what is claimed n certified

aquaphor
http://info.nsf.org/Certified/dwtu/Listing...ModlStd=ModlStd
ANSI 58

3M DWS2500
http://info.nsf.org/Certified/dwtu/Listing...ModlStd=ModlStd
ANSI 42, 53

espring
http://info.nsf.org/Certified/dwtu/Listing...ModlStd=ModlStd
ANSI 42, 53, 55, 401

if you do need more info, do pm,

Panasonic has a membrane for bacteria removal which 3M lacks. Will you be boiling anyway? What is your budget, give or take?