I'd like a bash at this:

Can we get some assumptions out in the open first...

And before I get toasted, I am not being patronising, I just like to get
assumptions clear and out in the open.

1. throughout we stick to one glider type which is, e.g.
i) why? because it would be like comparing apples and oranges otherwise
ii) so, lets assume it is an asw23, or it is a pik20b, or ...
ii) consider two cases: ballasted (= greater mass) and unballasted
iii) otherwise, the configuration of the two gliders is identical except for
the amount of ballast they are carrying

2. potential energy = mass x gravitational acceleration x height, so
i) for a given height the ballasted glider has more potential energy than the
unballasted glider

3. kinetic energy = 1/2 x mass x speed x speed, so
ii) for a given speed the ballasted glider has more kinetic energy than the
unballasted glider

4. total energy = potential energy + kinetic energy
i) from the above we now know that, for a given height and speed, the
ballasted glider has a greater total energy than the unballasted glider

5. from the gliders polar and the basic arithmetic of ballasting we know that,
above a certain speed (i.e. the speed at which the sink rates of both the
ballasted and unballasted gliders are the same), the ballasted glider will be
travelling faster, for a given sink rate (= rate of energy loss), than the
unballasted glider, below that speed the unballasted glider will be losing
energy at a lower rate than the ballasted glider
i) this effect is due to the increase in the wing loading of the glider
ii) the same effect would apply (approximately, because the wing bending
would be somewhat different) to the unballasted glider in accelerated flight
(e.g. during a pull up)
iii) assuming the above, for a given speed the ballasted glider will be
sinking at a lower rate than the unballasted glider (e.g. the rate of energy
loss is lower) - don't believe me? look at the polar

6. provided we stay above that "certain speed" (which is determined by the
wing loading and so will be higher if the wing loading is higher)
i) for a given speed the ballasted glider will always be losing (potential)
energy at a lower rate than the unballasted glider
ii) this will be true regardless of whether the glider is in steady (i.e.
straight line) flight or in accelerated (e.g. turning or pulling up) flight
iii) in fact the difference in the rates of loss will be even greater in
accelerated flight

So far, so good (I hope). Now lets ignore the glide segment and just consider
the pull up and the subsequent zoom.

7. for two real gliders, of the same type, same configuration, one ballasted
more than the other, during the pull up
i) assuming the two gliders start at the same height and the same speed
ii) both gliders increase their wing loading in the same proportion to their
mass during the pull up
iii) I think that, given ii, they will follow the same pull up curve as a
result, but
iv) throughout the maneuvre, the ballasted glider will be losing energy at a
lower rate than the unballasted glider
v) so it should come out of the pull up higher and having lost less energy
than the unballasted glider (i.e. it will start the zoom faster than the
unballasted glider)

8. during the zoom (at zero g), if both gliders started at the same height and
speed
i) both will gain potential energy, and
ii) both will lose kinetic energy, but at a rate proportional to their masses
due to the effect of gravitational acceleration, and so
iii) the gliders would rise to the same height if they were in a vacuum
throughout, but
iv) they are not in a vacuum, they are gliding (probably at a reduced wing
loading), so
v) provided they are flying above that "certain speed", the ballasted glider
will be losing energy at a lower rate than the unballasted glider, and so it
will zoom higher

I admit this is a somewhat qualitative argument, so would someone like to put
figures on it?

Rgds,

Derrick.