DNS lookup times are strongly affected by things entirely within the control of DNS content publishers and nothing to do with what one uses locally, namely whether "glue" is in-bailiwick. Out-of-bailiwick glue causes a massive explosion of additional back-end queries.
This has been a known problem for decades, people having encouraged in-bailiwick "glue" since at least the turn of the century. If you want to decrease lookup times, add your voice to encouraging this. Experts in the field are nowadays generally persuaded that it is a good thing, which took a saddening amount of persuasion. But everyday administrators still too-often do not get encouraged to use in-bailiwick delegations.