Reaktor really is the end-all when it comes to software imo. I can't wrap my head around building from scratch in it, but I have a friend who has created some amazing ensembles. Some of it is just untouchable.
Still, I have not heard a software synth that can truly emulate the sound of a real analog 303. I've heard some good emulations of certain types of analog sounds you can pull out of a Minimoog, but nothing that has the true analog grind and versatility. I also love my Access Virus TI, which is now my go-to digital synth, despite it being the most unreliable and problematic piece of hardware I've owned. Massive is awesome, but I'll almost always run to the Virus instead.
But yeah... it's true, anyone who says that software is "inferior" on some basic level to analog hardware has their head up their ass. Once I take a break from the "rock" album I've been working on, I'm going to try putting together a minimal ambient album using only iPad synths. Really, the iPad is starting to shine as an essential piece of kit.