I have read the first 2 or 3 volumes of Yotsuba a long time ago.
Mmm, it’s hard to say. Yotsuba has a lot of broken grammar and slang, but, as a manga, gets a lot of visual cue. 時をかける少女 isn’t bad in terms of grammar and vocab, but still, it’s a book, and a bit dated at that. The way people talk feels a bit stiff nowadays, which can also be a challenge, depending on your background.
I think the best is to look at the sample pages (accessible from the home thread of the book if I remember correctly) and check for yourself.