Advice please: best potting compost brands

I'm gardening a lot in containers and have tried a few different brands last year. When I was reporting some of my plants this spring I found there was quite a difference in how healthy their root system are and those with a good root system were the ones that performed best last year and came back strong this year, obviously
. So I'm keen to find the best potting compost brand on the market that I can amend when necessary to use for all future projects. What I have noticed that the compost used by professionals, the one you find in the nursery plant pot, is very different from the one offered for retail. Is that for a reason? I've heard that Sylvagrow is used by professionals but haven't tried it yet. Are there any experienced container gardeners out there who can point me into right direction? Any advice would be highly appreciated.
P.S. it should be sustainably produced.

P.S. it should be sustainably produced.
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At my local nursery they make their own. It makes sense for two reasons. It is much more economical. The main reason is that they know what is in it.
It's the best I've used in a long time
PS - it does contain some peat
Billericay - Essex
Knowledge is knowing that a tomato is a fruit.
Wisdom is not putting it in a fruit salad.