As a simplified model for proliferating motile individuals, we introduce an active system of interacting particles with birth-death dynamics and volume exclusion. We consider particles with two different sizes and characterize the phase diagram in terms of all the parameters of the system (self-propulsion velocities, diffusivities and growth rates). In particular, we explore the conditions to reach coexistence between the two types of particles (large and small size). Specifically, we show that faster diffusion confers a competitive advantage, allowing larger particles to coexist or even dominate over smaller ones in the long run. The case of activity is more complex and the different outcomes will be detailed in the presentation, in particular when Motility Induced Phase Separation (MIPS) is observed in the system. Finally, we will present preliminary results obtained by modifying birth and death rates based on the types of particles surrounding them.