The short answer is not very reliable. Here's why.

First of all, ground attack aircraft are guaranteed to be shot at by at least something. Whether it's AA machineguns on the tanks, dedicated AA vehicles following them, enemy fighters, you name it. There isn't much time to carefully line up a strafing run and then stick around to examine your results. Also, if you see a tank stop, what does that mean? Did you destroy it? Knock it out temporarily? Did it drive off the road to escape your attack and become bogged down? There is no way to know. Also, since you are not a ground unit, the chances of you capturing the battlefield and evaluating the kills up close are almost zero. This leads to situations described here. Between June 1950 and June 1952, the US Air Force makes claims of 1256 tanks destroyed and 1298 tanks damaged in Korea, while the most generous intelligence estimates credit the enemy with 600-700 tanks. That's the first problem.

The second problem is a systematic issue of overclaim in the German army. I've only researched it in the context of tank-on-tank action, but according to Joachim Peiper, this problem was an epidemic that gripped the entire army.

Assessing numbers in the air war was difficult at the time due to ordinary "fog of war" and hasn't been made easier with the passage of time.

I am not aware of a source that critically examine's Rudel's claims. I read Rudel's account and it took the claims at face value, as is only natural. There is no reason that we should however, since almost all air claims in WWII overstated losses by a hefty margin.

It wouldn't surprise me if the first source you linked on this subject (which itself sites decent sources) is the best available discussion of the subject available in English. The 10x ratio of claims/losses given in the example is pretty normal for WWII. Fighter pilot claims of kills usually can be discounted by about a factor of 10.

So I think I'd find the first article convincing and discount Rudels claims by a good margin.

Having said all this, I think the author of the first article overstates his conclusions, the effects of air attacks and air interdiction did seem to markedly reduce the combat effectiveness of armored units and the fact was extensively noted by contemporary officers.

I have read about trials conducted by Soviets, Germans and the Allies that show how difficult it was to even damage tanks with bombs

Most of the tank kills credited to Rudel were not with bombs but with the dedicated tank killing Ju 87 G model of the Stuka armed with two 37mm antitank cannon in pods under the wings.