We have agonised over this a bit, and although both have points to recommend them, on balance we feel that Medo does a better all round job as a sealer. We, therefore, no longer stock Seal n Heal and recommend Medo in its place.
Pruning compounds are used to seal up the cuts caused by pruning or other damage to your trees, protecting the tree until it produces its own natural callus.
A tree forms a natural callus by growing bark over wounds - you can see this clearly on any tree that has had branches chopped off a few years ago.
Until that callus has formed, a wound is a weak point in the tree's defences against infection. The main risks are bacterial cankers (which can attack almost any tree), Silverleaf which kills stone fruits such as plums and cherries, and coral spot.
They should be re-applied annually until the bark has regrown.
You can buy more garden fertilisers & chemicals here.