I installed my first Plastimayd  liner twenty-some years ago.      It fit perfectly, in spite of me.  Over the years, I have installed many other brands of liners, and, in my opinion, Plastimayd is the best.  Their Ultramayd is a Really Great liner, I actually prefer it over the heavier weights, and they are about the same price.  They can make a liner for just about any pool, and if the pool is measured  correctly, they  "fit so perfectly, you'd think we used a brush".

One good reason to buy a particular brand or style of liner is for it's longevity.  But that is not the only reason......There is also style.   If the liner you like is an Ultramayd, that is a very wise choice. They are more resistant to chemical damage, and UV rays.  But if the one you really LOVE is only available in the 20 mil, then by no means rule it out.  All Plastimayd liners are constructed with top notch materials, and excellent manufacturing.

In a way, what you are paying for in the Ultramayd and Perma-wall, is a little forgiveness for less than Ideal water chemistry, and for living here in Oklahoma where the sun, snow and wind all take their toll on even the best of vinyl.

By the way, one of the worst things you can do to a liner is to let the pool turn green, leave it that way, and then clear it up with cheap shock.

When choosing a pattern, of course, most important is what you like......unless you plan to sell the house within 5 years. Then, you want to choose what the majority of prospective buyers might want.  Also, if your coping is not perfectly flat and level, you can make it less noticeable by choosing a liner that has fewer straight horizontal lines in the "tile". The pool is usually the most dominant feature in the yard, and liner replacement is a very effective remodeling tool!  many savvy sellers replace  usable pool liners along with the carpet before showing their homes.

You can learn lots more about Plastimayd on their website,

http://www.plastimayd.com/