Based on your risk preferences and drip contributions go with the company scheme. It’s just easier with regard to tax, basically you pay in (they may do some matching of your contributions as well as regular monthly payments) and all the tax is sorted out monthly vs stand alone avc where you may have to claim tax back at the end of the year.
One other note the new scheme should be separate, do not mess about with the defined benefit one and definitely not unless you have advice you can trust. They are like gold dust and it’s highly unlikely you can do better than the pension they will pay you so leave it alone, I’ve heard stories of “advisers” and companies trying to get employees to encase or transfer them when it’s almost certain they are best left alone.