Both are stories about the JSDF. Both anime try to be about interpersonal (and personal) struggles within a military setting. Rescue Wings is the better show undoubtedly, but both provide a unique experience. Anyone who liked HisoMaso will probably like Rescue Wings because of the similar setting and focus on characters.
Well they both have these half-mech half-living beings that they control from the inside, a tsundere character with a Napoleon complex who feels outdone by the protagonist and a protagonist with personal issues which (s)he will resolve by being a pilot.
While the two are significantly different in the character department, both have a similar atmosphere with their general lack of serious drama. That might be an advantage or disadvantage depending on personal preference. HisoMaso tells a slightly more serious story, though, where characters have to cope with their self-esteem issues through piloting, while Dragon Maid is more focused on daily dragon hijinks.
Oh yeah, and both have moe dragons. If that's your thing, go watch both.
Both are military slice of life anime at their core, So Ra No Wo To is generally more serious in tone though. Both focus on a character that is severely under-prepared for military life, but So Ra No Wo To doesn't put so much focus on one main character. Regardless of minor differences, you should enjoy both if you're one to like military anime.
WAIT WAIT BEFORE YOU RUN UP ON ME. I don't care about your opinion on Franxx because at this point, It's very hard to not notice similarities.
-Both shows has the underlining theme of finding strength with the people around you
-Both shows have light sexual harassment.
-Both shows use "love" or romantic relationships impossible to occur due to the main characters profession.
-Not to mention the staffs of both shows being involved in Neon Genesis Evangelion
In my opinion, I think Hismaso is far better than Franxx due to it's writing and more likable characters.
Both shows have a cast of characters that have broken or dysfunctional traits who are sucked into a program that intends to give them a purpose or goal. Both series also share the same director and script writer.
They share the Shinto imagery of a ritual or a being which must be appeased through a form of sacrifice. Each show has a team of girls who are to be loyal only to their respective jobs. Yuuki Yuuna is a take on the dark magical girl genre, while HisoMaso has a more light hearted take where girls are joined by dragons.