Not the first time and will not be the last some seller just like to twist and turn.  All because they sell the specific products. Buyer need to do own homework and survey.

For drinking water,  If have the budget go with amway,  3m also not bad,  and I have friend using Tupperware water filter is good too. Especially filters come with proper certifications loke nsf. If want economical there tons of brands out there, and many are oem from the few big factory. Even Panasonic are good.

My mom still using first generation amway uv filters,  and I am using for indoor and outdoor.

Nope, only the drinking water filter. Everyday at my mom house also drinking the water from the first gen Amway UV filter. Earlier day we had to replace the filter very frequent because the outdoor filter really F-up, and outdoor was  sand filter, dam lousy and changed 2 brand. After change to membrane filter is so much better.

0.01 micron for an outdoor filter (POE = Point of Entry) is usually not recommended, as it also remove chlorine from the water that enters your home which you wish to all the Chlorine to go to your water tank to continue to have the benefits of chlorine as a very cost effective anti bacterial agent.

(1) Some ppl who have used membrane type with 0.01 micron as POE for a long time, experience algae growing in the water tank and causing a lot of problems in the piping.

(2) Some membrane type POE filter got problem after 1-2 years of usage in areas with higher water pressure.
For POE,  sand based water filter are more suitable, mostly due to reason (1).

When come to POU (Point Of Usage), you want to remove all the cholorine, heavy metal, VOC, TTHM, lead, mercury, Benzene...a long list of contaminants.

Do watch out for microcystin too, something new that by boiling water to 300 C won't remove it still...this is new standard published in April 2016.

My mom house changed to membrane outdoor filter is work far better than the sand filter we had before.  I think in Malaysia, is unavoidable to pay tax, toll, and water filter.

sand filter is filter with sand. Only 3 OEM out there. They are all the same.

All structure is made by these OEM. Brand differential is by custom casing and filler. Piece of advise, keep it simple, dont fall for gimmick and pay more attention on how to make installation compact and nice looking.