Timestamp vs timestamptz

Hi,
I'm working on a web project with pgsql, i did use mysql before and
stored epoch in database so i'm not familiar with these datatypes.

What i wanna ask is, if i don't need to display timestamps in different
timezones, shall i use timestamptz anyway? I mean, i'm gonna need
timestamp columns on some tables for internal calculations and stuff
like delaying actions, adding a row with a timestamp of 10 minutes
later and check for them every minute, fetch elapsed ones and process,
not to display them to users.

Will there be any advantages of using timestamptz type for this? I
thought, only if i move the website to some other server with another
timezone or something, all my timestamps and delayed actions would
still be accurate to the system clock..

Shall i just use timestmap type or timestamptz for this? 

Thanks.