The loose form of the variant, in which Totteridge & Whetstone is not allowed to be blocked, is considered by many to be a rather boring game.
The strict form is generally held as altogether more exciting. It does not allow deviation from the limited subset of strategies Allbright considered for developing the Totteridge & Whetstone line of play. This means you only have a choice of three moves for each position, bifurcation (and beyond) is disallowed, loops are impossible, and there are various other minor side-effects too.
[Darren]