I like the thicker outlines to the lineless (or whatever you want to call it :P). But I guess that's a thing of personal taste. And it's not a big enough change to make me say "I dislike it" because I love them both, I just like one the tiniest bit more because I find thick outlines really appealing in an art style.

However, if you had drawn the following image in a lineless style and a thick-lined style I'd prefer the lineless because of the scene it depicts working better in that style.
http://www.furaffinity.net/view/24085239/

tl;dr IDK, it's my honest opinion, but I really like both almost equally so saying there's an improvement is apples to oranges :P

My goal is to establish a style for comics just like I tested in that panel. You'll see a real test soon.
I know some people prefer my older style but I'm honestly sick of it. It was my style for several years and I was getting very frustrated for failing accomplishing a better one. This is the result of several months of unseen practice.

I'm very happy for this and love drawing with it. I dislike inking (several artists know that pain) and this art style has none, which makes the whole process fun.

Well, if it makes it fun for you, who am I to judge?

While both versions are very good, the later works in the lineless style are more painterly and have a better dynamic tension, in my opinion

Yeah because it accomplishes what I couldn't before.
And after several years in the same style you feel like changing.

both style have their own positive point. for me remember me this both style on game graphic how hard shading with thick lines and soft shading with thin lines or complete without lines.