Wrong, because most twin engine fighters are designed to carry more internal fuel, which equals the fuel fraction again:
Gripen NG - fuel fraction 0.32
F16 Block 60 - fuel fraction 0.25
Rafale - fuel fraction 0.33
F18SH - fuel fraction 0.32
The performance during peace time is not an issue, because you calculate that before you buy these fighters. You will buy them only if you can afford to operate them. If that is the case and you have an operational requirement for it (be it in air superiority role, or strikes), there should be no doubt, that any AF would opt for a twin engine version, if they have the choice.
Debatable, because it depends on the fighter designs:
Length: F16 - 15.03m / Rafale - 15.27m / J10 - 15.50m
Wingspan: F16 - 10.00m / Rafale - 10.80m / J10 - 9.70m
Height: F16IN - 5.09m / Rafale - 5.34m / J10 - 4.78m
Empty weight: F16IN - 9979 kg / Rafale - 9500 kg / J10 - 9750Kg
MTOW: F16IN - 21800Kg / Rafale - 24500Kg / J10 - 19277Kg
As you can see on the pics, it's not the twin engine that makes Rafale more visible, but the different wing design. If we now consider the J10 besides the Rafale, we would hardly see a difference.
An F16 IN is expected between $50 and 60 million dollar fly away, the Rafale around $85 millions. The maintenance of the single engine fighter is of course cheaper, but if you loose one fighter due to engine failure, you lost $50 to 60 million dollar. The Rafale on the other side, has good chances to return home, even with 1 engine, now how much higher must be the operational costs of the Rafale, to equal the loss of around $30 millions?
More importantly, you started with the statement that you want capability for your money, but here is the problem. A Rafale can carry more load and will offer better performance with higher loads, exactly because of the higher thrust of 2 engines (F16 B60 dry thrust, 84kN, Rafale dry thrust 100kN) and bigger twin engine fighters like F15, or Flankers will be even better in this field. They can carry more fuel and loads, while offer better thrust performance than a single engine opponent, which clearly makes it more capable.
The bottom line is, it's not that easy to say where the advantages of single, or twin engine fighter lies. The engine technology has matured during the past decades and especially the western engines are very reliable now, but you can't rule out a loss of a fighter and you can't generalise it either.
The US forces are stating, that the single engine F35, will be up to 1.5 times costlier to operate than the twin engine F18 Hornet it will replace.
Dassault has developed the twin engine Rafale, based on operational and maintenance routines of the single engine Mirage 2000. They say that it needs 25% less ground crew to maintain the Rafale and the operational costs are said to be just 12 to 15% higher.
