I just want to say that you're missing out a lot if you're still on artrage 4.
artrage 5 itself was a very massive upgrade, 6 kind of felt like an expansion pack for artrage 5 - I upgraded to 5 very fast, but hesitated with upgrading to 6, and I kinda regret being late.
the performance is better (particularly, better than 4), you can work with several documents at once, and there's a very impressive custom brush tool, that got a paint depth support in artrage 6. it literally kills any other app out there on the market trying to simulate thick paint, and I more or less tried them all.
paintstorm and clip studio are both very lovely (I dab into storm once in a while, and CSP is my 2nd go-to painting app), but there's really nothing out there comparable to artrage once you get hooked on it. it has its downsides, but it pioneered so much stuff in the real-media CG painting apps, and when artrage does things right, there's really no competition to me tbh.
it's not a photoshop killer, or not a jack of all trades like paintstorm, krita, affinity, etc., but it still excels at paint simulation.