Oval word bubbles are WAY better than the boxes. This has been a fact for almost a full century. I used the boxes for so long in the sprite comics because they were quick and dirty in MS-Paint XP/Vista and there was no center text tool. They also were very compact and worked well for the constant 320x200 panels. These ones are significantly larger but easier to read, and I can be far more flexible with text size and tone.
It also makes walls of text (Page 17 for example) so, so much more bearable.