Hi,
I was curious why does 'pacman -Q' operations took longer than 'apt' counterparts. Sounds interesting but I have a few question about how did you measure this and how big the difference is. (Shouldn't be that big). Would be great if you provide more information on the comparability of you systems and the tools you used for tracing. Maybe there are other reasons why it is slow on your installation ?
For long term pacman development road map, it would be better to use single sql based database for tracking locally installed packages instead of keeping directories of every installed packages. I am not sure if a sql based database would be a good solution if you where right. It adds much more complexity and also a dependencies on $SQL backend. For me as a semi-professional arch user this would be worse than a maybe "not that fast" package dB querying.
Regards, Robin