Pension/retirement arrangements where the contributions are defined but the benefits are not are a risk to the individual -- you have to figure out "how much do I want to invest, what do I think the market will do, where should I put the money?", and if you get it wrong you don't have enough money in retirement. For the company, on the other hand, they're very low risk, because the amount of the company's liability is clearly defined and limited up front.
Arrangements where the benefits are defined are not a risk to the individual (who knows how much they will get, and will get it regardless of market conditions over the next few decades); instead they're a risk to the company/government/etc that provides them (if they set the defined final pension too high and investments don't go so well then it costs the company more than they expected).
In general my preference is that (as a society) we should prefer to impose risks not on individuals but on large organizations who can afford to employ people who take the time to assess those risks and make the necessary decisions, and who have the resources and timescales to be able to weather unexpected downturns. So I think defined-benefit is better than defined-contribution.
(This is of course entirely not the way the pension setup has gone, at least in the UK -- defined-benefit is getting rarer and rarer, and defined-contribution is pretty much the standard for the private sector these days. But I think it's an unfortunate trend.)