[CurryLover]

The answer to your question is that it depends...

Heads up against each other the A4 is a favourite, obviously.

Heads up against another hand - it depends what that other hand is. If you are heads up against a big Ace, like AK, AJ or AT (but not AQ obviously) then QTs has better odds than A4o. If you are heads up against a pair then you would prefer QTs against all pairs lower than a T, and prefer A4 against higher pairs (against AA you'd prefer to have QTs).

In general, in multi-way pots the QT is better. If you play QTs and A4o against 8 other random hands to the river (assume all hands see the river), the QTs will win a higher percentage of pots than the A4o.

So, even though A4o is a favourite heads up against QTs, it is actually a worse hand in most situations.

The value of a hand changes a lot depending on the situation and how many opponents. For example, everyone knows that 22 is a slight favourite over AK if played all the way to the river. However, if you have a three-way pot with 22 against AK and, say, JT (or two other overcards), the 22 is actually in bad shape. In this 3 handed situation the AK will win the biggest percentage of pots, even though it is a small dog heads up against 22.