They're not as good value, per £100k of pot, as a typical DB pension is per £100k of notional transfer value. It's another way that DC pensions shaft you compared to DB.
Because my employer has buggered up our pensions by changing schemes over the years, I have a big DB plan and TWO smallish DC plans, although I have never worked for anyone else. I really want to take all the cash free lump sum from the crappy DC plans and clear them out, but HMRC doesn't allow plans to be aggregated even though they're all from the same employer and continuous service. One is just under £20k so I may be able to empty that under the small pensions rule. However, I'm going to have to take some tax-free cash from the DB fund, which means replacing the income it would have given me with "something" from what's left in the DC fund(s). Could be drawdown, could be annuity. I don't like risk and no-one really needs the inheritance, so I may have an annuity.