The floor dumbbell presses are great if you have existing shoulder pain, particularly in your internal rotators, as it limits ROM. I have seen Jeff Cavalier (AthleanX on Youtube, check him out! He’s awesome) perform a dumbbell on the floor and he explains that it is safer to do flyes on the floor as it limits ROM and protects your shoulders - though he is not a fan of the conventional flyes.
You may incorporate both into your workout! You can perform the push ups as your “usual bench press” while the floor dumbbell can be unilateral work. This can give you more volume as well as you are looking at muscle hypertrophy. There is no one exercise that can cause you to gain muscles but the overall volume (sets x reps) you do for the muscle group, the manner in which you do (eccentric contraction can can elicit more mechanical damage to your muscles) and your diet.
Gradually overload your body to challenge it and it will adapt. Our body is a use it or lose it system. You can do a variation of push ups - body horizontal, incline and decline; explosive; archers; etc. I can write another post on them 😂 When you challenge your body hard enough, it will have to adapt and if the nutrients are sufficient, your muscles will grow!