Both of them are autobiographical accounts of their authors' (both of whom being female) experiences with subjects related to the LGBT community with a comedic edge. In Hanayome's case, it deals with the author being a transwoman and Sabishisugite deals with the author's experience of being a lesbian.
If you've enjoyed one, you're definitely going to enjoy the other. Both manga are written by the mangaka who have written about very private experiences of their lives, resulting in unexpected turns and twists of life. Low self esteem, poor confidence levels, the fear of being judged by society, struggling about not being "normal" and other similar topics are touched in both the manga. The art in both is kinda cartoon/stick figure type, because the emphasis is on the story telling and sharing the intensely private experiences of the mangaka.
Both are kinda funny and loads of people have found the experiences mentioned in them as relatable (not me, tho :/) read more
Both are manga that deal with themes of depression, yet go off on their different ways as interesting character-driven stories. You are not guaranteed to have a good time reading through either of these, but it's a very accurate depiction of what depression does to a person. Worth your time.
Both talk about self-knowledge, sexuality and other emotions with deep psychological aspect. Is interesting see the different visions of the world that make different the two series. Inside Mari is more tense and heavier than Sabishisugite, but even so a great manga.
Both of this series deal with lgbt issues in a different, more mature and relatable way, which lgbt people themselves can feel identified with.
The main difference is that Shimanami tasogare has a much more dramatic atmosphere; whereas My lesbian experince with loneliness is more comedic, which, in my opinion, is for relief, since it deals with very sensitive and heavy topics, and it is an autobiography. Of course, this doesn't mean it shouldn't be taken seriously.
Sabishi is more about the inner struggles of the female protagonist. It's based on her real-life experiences, is much darker because of it. Not even close to Yaoi or Bara but if you enjoyed th psychological/sociological aspects of Otouto you'll love this too.