China has somewhere between a 5-1 to a 10-1 advantage against Taiwan in just about anything you care to measure. And while 20-30 years ago Taiwan could depend on having better gear, the mainland has caught up and likely surpassed them just about everywhere as well.
But Taiwan still has four huge advantages in a theoretical war.
The first is the Mainland can’t throw everything at Taiwan. The vast majority of their forces would have to remain on their other borders. So while they have a 6-1 advantage in combat aircraft probably only about a third of them could be devoted to Taiwan.
Second, the strait is a huge barrier. China has well over a million men in their army. But at best they can sea lift about 30,000 of them. And that is pretty much counting even every theoretically amphibious capable ship. Which means Taiwan effectively outnumbers the Mainland 4-1 in ground forces that would actually be engaged.
Third, Taiwan gets to fight in a defensive posture over known and fortified ground. This gives their forces an advantage. Even in aircraft, although likely outnumbered, Taiwan will be fighting over their bases with anti-air missile support. Whereas the mainland fighters won’t have any support and will have to fight their way in to their targets.
Fourth, Taiwan would likely have the US as an ally in any conflict. And that may bring in other Pacific rim nations in as well. Fighting through the US 7th fleet and maybe the Japanese as well as Taiwan’s navy means that China is going to have a hard time even landing their outnumbered ground forces.
All in all I wouldn’t give then a chance in a hundred.
That said that doesn’t mean China isn’t a first class military power. They have the largest army in the world. And significant portions of it are fully the equal of the US in training and equipment. They are still lagging in command and control. And they are in transition from a mass division based force to a more agile brigade based force (like the US). But where they have modernized they look to be very effective.
The navy is also in the middle of a huge transition. They are trying to create a true blue water navy. And so far are pulling it off. As it stands they definitely in the top five naval powers and within 20 years look to be number two. 20 years ago they couldn’t operate outside their adjacent seas. Now they have a permanent presence in the Indian Ocean. And that is the kind of navy they are looking to build.
Likewise they currently in third place for 4th generation fighters. And are one of only 3 countries working on a 4th generation fighter.
Even with friendly nations to base from they couldn’t pull off an invasion of Iraq like the US did. They don’t have the transport or logistic capability. But they probably could have occupied it better. And as a whole they are rapidly improving. Given another 20 years they may be able to insert and support 20 odd brigades anywhere in the world. All in all they are not the match of the US more or less in any category. And there are some categories that they are quite deficient in. But they aggressively working on everything. The US looks to still be the gold standard for the foreseeable future. But I expect anywhere China isn’t already number two they soon will be.