i would definitly micro chip as it only increases the chance of getting ur dog back if lost....so thats only an advantage.

The needle isnt as big as it might sound .... its bigger than an usuall needle but the pet doesnt really feel it when done properly.
I first myself was a bit worried but its not as bad as i imagined

I had my cats micro chipped and they didnt even felt anything happened to them so i guess a small dog shouldnt feel as much pain