It depends entirely on your use case. If you travel very frequently and want a watch that is only practical when you’re crossing time zones, then get a traveler GMT. If you spend more time and home while needing to frequently monitor other time zones, then get a caller GMT. Neither is a “true” GMT.
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i prefer caller for my use case which is tracking the time zone of a relative living outside the U.S.
I prefer caller, and to be fair, I don't understand why one would want a traveller.
I use the hour hand for my home time, and I move the GMT hand for the time of where I am going when travelling.
On the budget side citizen has the bj7100 and other similar gmts. These are traveler's gmt's and also don't stop the time when adjusting the hour hand to the new timezone so the timekeeping is not affected by changing timezones.
If you're actively crossing time zones, you absolutely want the traveler. But if you're just sitting at home or at a desk and want to track a second time zone, the caller will serve you fine.