Both the Romulans and the Klingons have the benefit of being much older nations which I think explains how they're still competitive with the Federation - they've had more time to conquer and invent. The Klingons also have the benefit of alien tech early on via the Hur'q. Still, given the UFP is already ahead of them, I see the gap only widening the further ahead in the future you go. Cooperation, science, and altruism are more efficient and competitive than force, threat, and anger.
Logically, the Federation should have the fastest tech level increases with the way their society is structured. The cooperation of over 150 species in all aspects of science, tech, and everything else in life is really quite a sight to behold from a long term perspective.
We don't really know how advanced other species are. The fact that Federation is dominated by humans would mean that humans are probably the most advanced species. Other species might be similar to stagnant Bajorans. That's why I don't put much stock into the 150 creative species theory. It might give Federation slight edge, but don't underestimate the power of disciplined totalitarian states like Romulans/Cardassians to make significant advances on their own.
Japanese and Germans in WWII made significant advancements in only a few years. Germans perfected the armored warfare and had best tank in the war. Japanese had biggest/may be best battleship. Soviets, through sheer numbers and industrial strength (their own and US's) pushed back more advanced Germans. Later on, they kept up with the resource-rich US just fine for decades.
For all we know, an old civilization like Klingons could be spread over 50,000 planets and outnumber young humans and most of their other members 10-1 in sheer manpower. This alone could make up for their lack of industrial efficiency and scientific diversity. Look at the standard of living in US compared to China, but Chinese are doing a good job of keeping up industrially, and may be they're even ahead of US in that area.
Being Taiwanese, I know for a fact that the China is a rising economic power, but there technical capabilities leave a lot to be desired. What they do is copy whatever they are taught. They have a very hard time innovating on their own.
They also like to skimp on areas whenever possible.
Look at a Chinese made car being tested for safety.
Would you pay money for a car of that safety caliber?
"Fordís market research found that as recently as 2006, safety ranked last among the nine most important attributes for Chinese car buyers. Although safety has moved up to sixth, the exterior appearance of a car was the top priority for buyers then and now. "
"Chinese regulators are putting pressure on Chinese automakers to strengthen their designs. They have begun issuing star ratings for safety to cars sold in China, after copying the test methods from the National Highway Traffic Safety Administration in the United States. "
We've had lots of 5 Star rated safe cars in the US for how long? China is starting to issue star ratings? WTF?