This is a poor comparison because of the big difference in these two aircraft.  Here are some numbers to help you understand the huge difference between these two fighters  (all the units are in pounds)

F-16XL:
 empty wt: 20,631
 Max T/O wt: 32,073
 Max internal fuel: 7,116
 max weapon load with max internal fuel: 4,326

F-18E:
 empty wt: 32,080
 Max T/O wt: 66,000
 Max internal fuel: 14,008
 max weapon load with max internal fuel: 19,912

And just for comparison purposes

F-15E
 empty wt: 32,000
 Max T/O wt: 81,000
 Max internal fuel: 13,123
 max weapon load with max internal fuel: 24,500

Some points to ponder:
 Payload has NOTHING to do with the number of hardpoints
 F-18E & F-15E EMPTY wt is essentially the same as F-16 MAXIMUM wt
 F-18E & F-15E carry about twice the internal fuel as F-16

F-15E with conformal fuel tanks can carry an additional 9400 lbs fuel (71% more)

Max combat radius depends HEAVILY on the weapon load out, not only in terms of weight, but also in terms of the drag of each weapon.  You cannot compare published max range figures because this is usually the max ferry range, ie max internal and external fuel, no weapons, and landing and refueling at the destination.  In combat you must use radius because you are obviously not going to land and refuel at the destination and the combat radius depends heavily on the load out.

F-16XL was not a "delta wing" aircraft.  It had a "cranked arrow" wing, which is a very heavily modified delta wing.  It was also  equipped with leading edge sucking to maintain laminar flow.  It worked well until the microscopic suction holes got clogged, which in the real world was VERY often.  In other words, a great idea on paper and in a clean lab, but a lousy idea in the real, operational  world where  airplanes get dirty.

Consider that any early US and Russian fighter aircraft had delta wings.  Both the US and Russia have abaondoned the delta in their last TWO generations of fighter aircraft.  The Europeans have stuck to that wing planform, but attempted to improve their characteristics with the addition of canards in the Typhoon and Rafale.  Among other things, delta wings have high drag rise with increasing angle of attack (AOA).  AOA is by definition high in any high G maneuver.  The result is that deltas quickly lose speed in any turn, so sustained turn rate suffers.  In addition, this places the fighter in a low Q (low energy state) condition in situations which require high loading (G), and for combat fighters, low Q is death in most combat situations.