According to goo, We can say 「彼を訪ねる」 but not 「彼を訪れる」 and we should instead say 「彼の家を訪れる」if we use the verb 訪れる. Does it have a nuance? Does it open the doors to another interpretation(visiting his house instead of visiting him for example)?
I know this classification is debatable, but 訪れる is JLPT 1 and 訪ねる is JLPT 4 on jisho.org, is 訪れる more formal or rare than 訪ねる?
Regarding frequency first, 訪れる is roughly three times more common than 訪ねる on BCCWJ. 訪れる is seven times more common if we limit the results to Yahoo! blog/chiebukuro articles, which indicates 訪ねる is even less common in relatively casual written materials. I personally think you should master 訪れる first. But 訪ねる is not uncommon at all, and you may have to learn it before JLPT 1 level.
IMHO, ～を訪れる is a neutral word usable in business settings and other everyday situations. You can also say ～に訪れる. (Note that 訪ねる is not a keigo and you often have to use honorific いらっしゃる or humble 伺う/お邪魔する instead.)
On the other hand, when an object is a place name, I feel ～を訪ねる is a rather literary and somewhat "nostalgic" term typically used with historical attractions (石川啄木ゆかりの地を訪ねる), one's hometown (母校を訪ねる), temples/shrines (東北の神社を訪ねる旅), etc. Using it with nearby modern facilities (e.g. 駅前のクリニックを訪ねる) is fine in stiff novels, but it can sound a little off in ordinary blog articles and such.
