TZ is a classic, but I got really great at it and got bored with it. GB is not even a classic, it's punishing, and it's not even finished. Id say keep TZ till bored, sell it and get another BW classic or a JJP.
Quoted from northvibe:All opinions... but you know people get bored of games :-p this mentality convinced me to buy a FT and I hated that game unless I was drinking.
Tz is a fantastic deep game, lots of shots, lots to do, but can be very daunting. New players may not like it.
Gb prem is beautiful, lots of shots, good theme, you see a lot of the same modes. Can be very hard with drains and tight shots. However all the guys in my pin league love gb and keep wanting to play another.
Two games, both different. Really depends on what you are looking for in a game and your style.
I think money wise both are about the same at the moment.