Mar,
Generally a PRB is used to accept a Transfer Value from a previous pension scheme. Normally no further contributions are made.
A PRSA is a type on personal pension into which regular contributions can be made, by you and an a Employer. BUT any Employer contribution is treated as a BIK for tax purposes even if you subsequently get personal tax relief on the total contribution.
If your Employer is willing to match your contribution I suggest an Executive/ Directors Pension as it is better from a tax perspective (the employer contribution is not treated as a BIK).