The reason blender is the only open source 3d app you'd ever need is because it is 1,000 easier to make blender look/feel like Alladin, than to make Alladin have all the features that blender does.
That said, Alladin, Wings3d, DAZ studio, Sketchup all of those programs are good enough to use with Leadwerks. But still blender has the most features and best organization and support of all of them.
In my mind it just comes down to whether or not you want a complete 3d app with monster development or you want less complete one with much less development.
Alladin4d doesn't have 1/4 the features blender does.
Sketchup is great but it teaches you nontransferrable habits for teh most part. So to a newbie it's hard for me to recommend that one. Wings3d, has less features than Alladin4d probably and DAZ also doesn't have as many features.
You can use whatever you like with Leadwerks. But I simply could not ever recommend a 3d open source app over blender. Not without feeling like I'm being dishonest.
Now I would recommend, still, downloading sculptris over sculpting in blender. But blender's sculpting is improving all the time. Pretty soon I probably won't be able to recommend sculptris over blender any more.
It's not that I'm just a mindless blender idiot (I hope not). But that program really has Akira (you've seen that manga/movie )level of evolution going on. It changes so much one day to the next in so many different ways. It's hungry to evolve all the time and that's what it does. That's why it gets prominance in my mind over all others. Because it's more than earned that prominence.