Agreed, every beat I've ever made has started of with me hitting random notes in a semi-educated guess order until I find something I like. Thats more than likely a detriment in my case, but you gotta start somewhere I guess. Granted I know fuckall about what scales I'm playing, and even less with chords. 9 times out of 10 I'm stumbling through shit, I just know it when I hear it and what I want to hear next in line. The trick for me is finding that sound. I'm either 0% or I'm 100% and the beat is almost done in at most a few days. Almost every time I make something I'm happy with, the only way I can describe it is that the beat made itself, I just had to try to steer it in a direction that works.
Having said that, its pretty obvious to me that certain gear will affect your sound. It's also obvious that it's entirely due to workflow. Individual gear is good at what it's meant to do. Thats why you buy it. I wouldn't buy a keyboard if I just wanted to use it as a drum pad or to sample, and I wouldn't buy an MPC if I wanted to write the music myself, even though both can do what the other one does (persay). I think at the end of the day it still boils down to personal choice and what it is you want to make, and what's better situationally. To tie into the way the conversation was headed, its about the feeling. Neither are wrong, but both are right given the circumstances you use them.
As a footnote, i think that owning a keyboard is probably more versatile if that's all you can afford, mainly because you can map your keys to work as pads (and hell, a lot of em have pads on them anyway), but I won't say that you'd benefit from not buying the right gear for the job also.