Reference: Liqaa.aat al-Baab al-Maftooh – Volume 1, Page 54, Number 95
Question: What is best to do whilst travelling: combining the prayers at their earliest [permissible] time (jam’u taqdeem) or combining the prayers at their latest [permissible] time (jam’u ta.kheer)?
Response: That which is best whilst travelling, with respect to combining [the prayers], is to do that which is most easiest for you.
So, if it is easier for you to combine the prayers at their earliest [permissible] time, then do that. And if it is easier for you to combine the prayers at their latest [permissible] time, then do that.
The best is that which is easiest for you to do, whether at the earliest [permissible] time or at the latest [permissible] time – both are legislated for within the Sunnah.