I've never used Simunitions, but I have used ATI (same concept). I'd definitely say that using those kinds of munitions steps up your training game quite a bit. For me, it's similar in feel to paintball in that you know it's not lethal so you're free to test tactics and such, but by using your duty/EDC weapons things just feel more real. The training feel with UTI/Simunition rounds was the closest I've come to the real world un-holstered building and area sweeps adrenaline and stressors, but in a lead-free training environment.