First flight F5D April 1956.

F5D Skylancer
More capable than the F-11 Super Tiger.
A production order was put in but stopped after 4 aircraft mainly due to politics.

In what ways was the F-105 just as capable? Can’t be payload/range. Or avionics, think low level terrain following at night and in bad weather. Speed? The 111 is faster. Self defence? The 111 could outrun pretty much everything and could carry Sidewinders. Internal gun possible.
Just to give you some numbers: Ferry range for the F-105 with full internal (i.e. with weapons bay fuel) and external (3 tanks) fuel: 1917 nm. FB-111 ferry range without external, with weapons bay fuel: 3033 nm. 4313 nm with 6 drop tanks.

The question was you could only have one aircraft. The F-111 could only drop it bombs and runaway. It could not defend itself. It only had a gun if you put it in the bomb bay, reducing payload or fuel.
The T-Stick II F-105 was a night and all-weather capable aircraft. The Thud could perform close air support if necessary, the F-111 could not.
The F-111F ferry range with fuel tanks was 3,100nm with fuel tanks.
The F-105 with tanks had a ferry range of 2,080 and combat radius of 680 nm.
With the bomb load on the wings the F-111 was probably slower than the Thud with its load.
Not having the F-111, the USAF would have lost nothing, as the B-58 had terrain following radar before the F-111 ever flew and plans were drawn up for a TAC B-58 but R. Strange McNamara got a lot of people killed and forced the F-111 on the military.

Three Billboards outside Ebbing, Missouri.
Outside of the ignorant biased view by left wing Hollywood of anyone who live between New York and L.A. still a very, very good movie.

The F-102 and F-106 were interceptors, were not (at least in their production versions) multi-role aircraft. That in large part is why they weren’t sold to other nations.
There is a new book on the ‘106 which calls it “the world’s fastest single engine aircraft”. I’m sure that if true, it refers to production types and not one-off mods.

The F-4 was an interceptor turned into a fighter-bomber.
Tactical versions of the F-106 were on the board but never developed.
The Six had longer range, much higher cruise speed and better altitude performance than the F-4.
Had they put the F8U-3 version of the J75 in it , 29,500 lbs thrust vs 27,500 , it would have had a even higher top speed.
If you dig through the now hard to navigate F-106 site you will find reports of the Six hitting, at steady state, higher speeds and altitudes than the published limits.
Had the TAC version of the Six and the B-58 been produced R. Strange McNamara’s pet, F-111, that was a stupid idea would never have seen the light of day.

Fact Pres. Carter’s moronic action in Iran and Afghanistan led to Taliban and Al-Qaeda
Fact: the moronic actions of Bush and Obama were factors in the birthing of ISIS
Fact ISIS as it was is dead, Muslim militants will find something else.
Fact al the finger pointing here of U.S. bad because ; Russia badder because ; U.S. badderest because … is childish forum banter as the pathetic news sources, East or West know squat about what the U.S. and Russia are really saying to each other and how they view the future of Syria.

As oppossed to the fair-and-balanced view fed to americans where everything from Trump to Bernie Sanders, to widespread white supremacy and racism in the US is Russia’s fault?

That is an absolute fact.
Bush did it has been replaced by Putin did it.