Choosing firm

Dear Reader I am currently pursuing my articleship in Grant Thronton ( indirect tax) however my whole team, seniors basically are moving to BDO and I have got an offer to join IDT over there. Basically new team will come up here in GT and the outgoing ones would be making new team over there. So should I go along with the team or not? If brand of BDO is better or GT? If IDT practice over there? and what other things should I take in consideration while deciding from a trainee's perspective?