John Innes vs multi compost

Hi
I wonder if anyone would be kind enough to explain what the main differences are between the black soil like John Innes formulas and the "multi-compost" type which is lighter in colour and springier?
Perhaps more specifically, I have a small Leylandii screen on a balcony in 10 inch pots which I'm planning to move to 12inch ones that are currently in the multi-purpose compost. Would they be better off in the black John Innes soil ? And in general when to use soil like John Innes and when to use the compost stuff?
I've been searching around the internet for hours but haven't really found an answer to this - maybe its so simple nobody feel the need to explain!
Thanks in advance for any advice on this.
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flutterbye

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flutterbye;917926 Wrote:

Hi Flutterbye, It would take hours to answer your question about the pros and cons about John Innes compost v soiless, to cut a very long answer short, John Innes when made from GOOD loam probably has the edge but the modern soiless composts developed by the GCRI were all about weight !! With the introduction of containerisation of shrubs came a need for a lighter and cheaper compost. The difference in weight between 1000 pots of plants in John Innes and a modern soiless, doesnt compare when it comes to transport, its as simple as that ! Lannerman
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lannerman

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