Both mixes are exceptional.

In the first year, you'll probably see little difference in growth between the two mixes.
The Gritty Mix, however, really excels beyond that first year, and is especially suited to
woody plants that will spend 1 - 3 years in containers between re-potting...of course,
that doesn't absolve you of your re-potting duties if the plants outgrows the container volume
in that span of time ;-)

5-1-1 is generally more of a "warm season" mix because it provides more moisture.
But, as with the Gritty Mix, it is very adjustable - minor tinkering with the ratios or
ingredients can create the perfect amount of moisture retention for your particular climate.

To extend the life of 5-1-1:
1) Use an uncomposted bark.
2) Eliminate or reduce the peat moss.
3) Use fine bark dust instead of peat moss for "binding" and moisture retention.
4) Use durable ingredients such as turface, pumice, scoria instead of the peat moss fraction.
5) Use soluble synthetic fertilizer instead of organic fertilizer.

The outer limit of my particular long-life 5-1-1 is about 3 years, especially if the mix
is exposed to the elements (or if I use Fish Emulsion, as with my big outdoor Chainfern).

Josh

Thank you Josh! This is exactly what I was wondering :)

Here's a pic of some 5-1-1 from last year's containers.

If I were really pressed for money, I would simply screen and rinse this material
and then incorporate a fraction of this old mix with fresh ingredients. This year,
I even re-used some old mix directly for a Weeping Willow in a larger container -
Willows tolerate such awful soils that I have no doubt that mine will thrive even in
this recycled mix. I wouldn't do this with all my plants, though.