Hi,
Whats the job for? if its dispatch I would say choose plane-handling.
This is what I recall from when i worked at LHR.
(Servisair) Globeground aint been the same since Lufty pulled the plug. Having worked for them the training was excellent and most of the contracts were good. Obviuosly as a business it makes sense to win as many contracts as possible and as soon as the got into T3 they got a few "desirable" airlines.
PH seemed to have less contracts and concentrate on them. From the job speci they also seemed to have alot more duties ie filing flt plans and from what I heard paid more.
However they are part owned by Aviance so beware!!
Good luck.
WTD