Considering a butterfly chair  

I have never bought a new butterfly chair frame but I have gotten more than a dozen vintage ones at auctions over the years and there was a big difference in the diameter of the steel used---some quite thick, and at least one that was really quite scrawny. So that's something to look at if buying new---also check how well the welds are cleaned up. Some of my old ones are kind of blobby.

Now as for the sitting angle---that may vary from one maker to the next but you should be able to determine that from side shots of the frames if they are available. I don't remember any of mine standing out as being noticeably more upright or laid back than the others. I like a really lounge-y lounge chair, though. I have a Kofod-Larsen Hoop chair that I don't like to sit in at all because it's too upright. I love Butterfly chairs, though. I do think they're a bit uncomfortable if you sit square in them---maybe that's just me being too lazy to hold my head up, but I want a head rest at that angle. So I just sit in them sideways a little with my head leaning on the corner (?) and then they're perfect. I would not hesitate to put them in a setting where people will be conversing with each other.