ME...
Depends what you're trying to do.
Canard/deltas are rather nice for agility and STOL (factors in Gripen, Typhoon and Rafale) while buying you the benefits of a delta wing (light, low drag, space to hang stuff that goes bang without too much interference drag).
Classic, cranked or double deltas are nice for low drag and high volume. What you tend to run out of is control authority because all you've got is the trailing edge... the leading edge is good for increasing lift to some extent (although the sweep tends to be too high - if you look at the XL it's got LE flaps outboard), but hard to use differentially for control. So the trailing edge... which doesn't have a lot of moment arm... has to provide for pitch and roll, and it gets a bit overloaded.
For instance, Boeing's delta JSF design, in its Navy version, was going to use vortex flaps above the leading edge to boost lift. But the more they looked at the Navy's bring-back requirement, the bigger control surfaces they needed, in order to rotate the wing to get high lift... and the actuator weights got out of hand.