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
Tour Bite Soft 17