Hello there! I think the new, 1.4 version will give you the best experience since it's a really large and significantly improved and expanded version, it contains a lot more story, better gameplay, visuals and level design than the current 1.3.2 version.
Try to imagine what you played in 2D but as a 3D shooter, the update is only about 7 days away so it won't be long ;)
The new update takes place before the events of 2D game and it explains a lot of backstory, as you can see I also transferred it's artstyle to 3D, it also looks quite a lot better than the screenshots currently provided from 1.3.2 version (you can see old screenshots on main page) so the jump in quality between updates is pretty huge.