I know this thread has been dead for a while (yeah, I do have a bad habit of "zombie" posting), but I have recently done some reading on the Archduke's exploits, and while I don't think he was QUITE as good as the "Iron Duke," I think he is certainly worthy of comparison and perhaps on the same level as well.
Why do I think this? Simple; 1796 German campaign, which is often unfairly over-shadowed by (but almost as skillfully conducted as) Napoleon's Italian campaign that took place at the exact same time. Here, he was out-numbered, and faced by two different French armies (as Napoleon often was in Italy as well), led by Generals Jourdan and Moreau, respectively, both of whom were definitely abler than any of Napoleon's opponents in Italy. Charles went for Jourdan, defeated him in two separate engagements ( at Amberg and Wurzburg, respectively), both of which were won due to superb battlefield maneuvering. This pushed Jourdan back to the Rhine, and although Moreau was victorious against a separate Austrian army at Friedburg, Jourdan's defeat forced Moreau to retreat as well (due to the compromising gap now created between their armies). Moreau returned after re-organizing soon after, and again, defeated a separate Austrian covering force at Biberach. Hearing of this set-back, Charles quickly marched against Moreau, the latter fell back, and Charles caught up with him, defeated him at Emmendingen, and soon after beat him again at Schliengen. Charles pursued Moreau back to the Rhine, where the latter pressed for an armistice, which Charles favored, but which the Austrian government foolishly rejected. This excellent campaign of the Archduke put a temporary check to Napoleon's onslaught in Italy, preventing him from marching across the Alps and into Austria itself, since he had depended on the cooperation of Moreau in so doing. Bonus points? He was even younger than Napoleon.
He later conducted an able retreat before Napoleon after that general's victory at Rivoli (and the subsequent surrender of Mantua).
He later scored a few nice successes in 1799, in Italy and Switzerland (one of which was against Massena, another excellent commander).
In later years, it can probably be argued that he lacked the energy and skill which he had shown in the past, but he was still quite able, and his re-organization of the Austrian army as well as his victory against Napoleon himself at Aspern-Essling ( even if he certainly can be justifiably criticized for not following it up) do him great credit.
So I think, judging from many of the posts here, that the Archduke is quite underrated, and that he can fairly be ranked at the same level as Wellington.
No problem, I have a bad habit of zombie posting myself!
Interesting comparison between the two and I thank you for it. Quite a good read.