To my ear the Osc’s sound the same however the AR has different synth parameters specifically for drum sounds. Sample feature is a bit tacked on and lacking in controls. It will not replace your A4 or the Mpc. The MPC is much more of a sampler than the Rytm will ever be and the A4 is a better synth. The Rytm would make a great companion to these two but it wouldn’t replace them. And yes you can get nice bass, pads ,fx and leads out of the Rytm. IMO the Rytm does this well but the drum abilities are a bit disappointing. I seem to be the only one that thinks this tho.