I am thinking about buying slx/xt brakes ,what is the difference between them apart from small price increase ?

not much.

there isn’t really much difference between deore and xt…

there’ll be someone along shortly to tell you that you definitely need the bite point control adjustment knob.

I was recommended the XT’s but they were out of stock, IMO if the price difrerent is small why have the better ones ?

Bite point doesn’t do much on my xt’s. The screw holding the pads in is a little nicer than the split pin on six, but I’d just go six if buying again. The slx caliper is threaded to take a screw so you could put one in there later.

Is there a weight difference?

I’d go SLX simply because they don’t have the tacky looking chrome finish.