Kind of a general statement. You can get O rings in about 15 different kinds of material. If the o ring and the umbrella are made of the same material, say Buna n I don't think you will see a big change. as both have a temp rating of around 250 f . viton will get you to 350 f, teflon 500. So the bigger the gap from running to maximum you will see a longer service life. teflon on the other hand is non forgiving hard as hell and normally a one shot deal and a lot more money,it will work good as an umbrella as long as you can get it past the keeper groves without messing it up.
I figure your 1990 has 200,000Km+ on it.....The original seals lasted this long, no reason for another set not to last as long as you will be driving it
If the umbrella seal is The most up to date upgrade go with it. I would suspect that once the o ring failed the contamination will do the umbrella seal in or it will trap all the junk in there till the valve starts to stick or the piston frees it up
A lot of the time the home mechanic installs the O rings incorrectly. They put them on the valve stem, add the springs and then spring retainer cap and finally the keepers. This is the wrong way to do it. It should be springs, spring retainer, O ring ( fitted into the lower groove of the valve) and finally the keepers. When the valve spring compressor is released the O ring seals the area between the valve stem and the retainer. Oil that runs off the rocker then continues to run off over the edge of the spring retainer and misses the valve stem for the most part. (Stem needs some oil for lube purposes, but shouldn't be drowned with it.) Putting the O ring in the wrong position on the stem allows the oil to run down past the retainer, down the stem, over the O ring and get sucked in at the stem/guide clearance. When done correctly, the entire valve assembly acts like an umbrella seal. Umbrella seals work great if you have some wear at the guide/stem or have had the guides knurled, otherwise the O rings are the way to go.
With the stock system o rings work fine,you will find the old one brittle or broke and missing. Follow snipers way and it will be fine. On high lift cams there is not enough room in most cases between the guide and the retainer for a umbrella seal unless the machinist has turned down the guide just for these types of seals.
