First consider the affordability of AVC contributions in your current circumstances, then the tax relief advantages.
Personally, I feel it is a bit academic to start targeting fund values many years hence since rapid change is such a big feature of people's lives these days!
Check out the type of funds you can invest in in the company AVC scheme, then compare with PRSA AVC's available on the open market.
Then compare costs of company AVC v's open market AVC's. Often costs will be lower for company AVC. Occasionally people don't want their employer to know what pension planning they're doing so go open market for only that reason, but I can't see much sense in that!
These days, also, everyone seems to get hung up on costs & only costs, ie the "something for nothing" syndrome. Wishful thinking!
At the end of the day "Ye gets what ye pays for!", as Another John wisely pointed out! Best of luck.