the PST has a high SW which is a detriment on the serve. I usually used the PSLGT but pulled out the PSTs when I needed a boost in power. The PSLGT is a serve monster because the SW is so low and you can really rip the racquet through the swing.
The PSLGT plays well at low tensions with multis so there is a little more power to be had there. I had both in my bag until I started getting a little TE and have since changed to the PK Ki5 which seems to be right in the middle between the PST and the PSLGT.
3X PK Ki5 315 ::: 4X PSLGT and 1X PSL ::: 2X PSTGT and 1X PST
MCS mains and PPA crosses