Assertion (A): There are a number of differences between barristers and solicitors working in UK.
Reasoning (R):  The most important difference is that solicitor can appear in all courts while barristers can only appear in higher courts if they qualify to become barrister advocates.

A is correct but R is false.

Though there are a number of differences between barristers and solicitors, the most significant one is that barristers can appear in all courts while solicitors can only appear in higher courts if they qualify to become solicitor advocates.