We’ve slept on Murphy beds several times - I would prefer a Murphy over a sofa bed any day. The quality of the mattress can be thick and very good. Whereas a sofa bed mattress has to be thin in order to be able to fold up. I’m planning a road trip for 8 people currently and will not consider that a sofa bed is a viable option.
If I were you I would invest in the Murphy bed since it is a small space - it would give more flexibility as you noted. It would be more comfortable for guests who might be staying for multiple days and need the space. You might even find a deal on a used one.