My 0.02p here:
PROS:turns faster,less current drain,easier to work on and fit spares,weighs less,Comes out with 2 bolts.
CONS:Only has 2 brushes(wear faster),has bakerlite/plastic brush holder which breaks down with heat.Is not as heavy duty as the Bosch.
PROS:Heavy duty,Has 4 brushes which last longer,has metal brush holder,needs less maintenance.
Cons:weighs more,Is arkward to work on(Brushes and springs)Is not as efficient.Has 3 mounting points which necessitates front engine cover removal.
Notes:I have found on the Valeo if you drill the rivetts out that hold the 2 main halves together and grease well you will get much longer life out of the unit.
I have not changed the starter relay ever with either of these starters.
The later 4-valve valeos use exactly the same internals except the motor turns the other way(magnets are other way round).
Trying to re-glue the magnets is not recommended(they must be correctly polarised!!)