I'm not sure which is which, is R-Type horizontal? That's the one I like.
However, I think the last "all in" holy shit wowzers shooter of that style was probably Pulstar. There aren't a lot of them made after the PCE era so I do play a lot of the other type.
And yes, the horizontal ones are more obstical based, but I'm not sure how much that has to do with the format itself. Around the time horizontals died in the early/mid 90s, shooters went into hybernation in general, most of them not even getting home ports. Then by the time things got moving again in the DC era Cave had done a lot of work to change the scene to a more score/combo based way of doing things and they happen to prefer vertical stuff with zero obsticals. If the Nazca guys had had a hit with In the Hunt instead of Metal Slug things may have turned out differently.
Btw, "shmup" is stupid term. Quit it. It sounds like a bowel movement or a line of cologne marketed by the guys from Duck Dynasty. f*ck.
Not as stupid as playing the things stretched 4x in one direction and not at all in the other though, meaning that things traveling at a 45deg angle move faster left to right that they do up and down. I can see the interest in that, psychedelically speaking, or maybe as an extra challenging funhouse mode or something, but it's the video game equivalent to installing a nose bra on a sports car. All it does is identify the owner as someone who doesn't see what the point is in owning the thing they are so proud of in the first place.
You asked for it, what can I say...