Next year "load" funds in a 401(k) will have some explaining to do... specifically, from the 401(k) administrator, who will owe a fiduciary duty to plan participants starting 2017. To give a fake example, a 5% load S&P 500 fund is clearly worse than a no-load S&P 500 fund for the participant. Under a fiduciary standard, the 401(k) plan would have to pick what's in the participants best interest, and go with the equivalent no load fund. The example is fake to make it clear - most load funds are going to hint that they're worth the load.
Keep in mind "past performance does not necessarily predict future returns", or something similar that every fund prospectus must state, per SEC rules. So when you weigh a load fund vs a no-load fund, and you can't use past performance, there isn't much interesting about the load fund. You should aim for no-load funds with low fees. If my opinion, asking if a load is worth paying suggests you're already buying some marketing rather than making good decisions. So be wary of buying a load fund.