Buy with the new invoice. Secondly as for the choice between VXL and VXR, it should depend upon two things:
a) Your preference auto vs manual
b) Your budget.
When i was buying Alto initially i wanted to buy VXL because it was auto had power windows, ABS and also because my wife could also drive it however when prices rose it got out of my budget and i had to settle for VXR which isnt bad either but lacks power windows, abs and auto gear.