Compared to clipless, they suck.
Riding uphill, the big advantage is in the pull, and to ensure you don't slip out of toeclips, they have to be done up so tight you loose circulation. then you need to slacken them off when stopping. That's lots of fun when riding fixed, and you will learn how to trackstand very quickly.
If you have them loose, they stop your feet from sliding off, but are fairly useless in helping 'grip' the pedals. Plain spiky BMX pedals are better, but do a lovely job of 'decorating' your shin skin.
Their sole big advantage over SPD is in very cold conditions. A big set of toeclips can be used with insulated walking boots (advantage toeclips), and they don't have a chunk of steel mm away from your foot, sucking the heat out (advantage toeclips). But you can get most of that advantage with spiky pedals and not have the issue of ice rendering the straps unloosenable.