[achrystie]

I'll be a little more specific.

Silo strengths:
1) Better and more responsive sculpting tools.
2) Better support for polygon count, but not overly significant.
I can get 1.3 million and still navigate and work respectably in Silo, I can only go to about 700K in Hex before it becomes unusable.
3) Almost complete UI customization. You can basically "make" your interface, any way you want. Customize: Mouse assignments, Icons, and Keyboard shortcuts almost completely, and dock/free float entry windows wherever you'd like.
4) Retopology tools. The topology brush is much faster and more intuitive than its 1.42 counterpart, and if you don't like that, you can use surface snapping poly by poly to retopologize.
5) Better symmetry support with an almost completely removed center seam (one or two of the brush tools still have "some" trouble with crossing the center seam).
6) Sticky key support for certain tools, along with tool integration, such as: a cut tool that acts as a point to point, edge to edge, and multi type cutter AND a knife tool if needed, all the same tool.
7) Developers that actually respond to your posts, including bug reports, and try to resolve those issues, as well as give you some idea what is currently being worked on.
8) "Overall" very stable, I've used it for 12 hours straight without any crashes or major stopping points.
9) Intuitive feeling brush tools and adjustments (this is of course subjective).
10) A user plugin has already been written to direct link the Silo text and binary file formats to XSI.
11) An SDK in the pipeline for a 2.x release.
12) Really intuitive and easy to use unwrapping tools.
13) Placement and saving of custom light setups.
14) Potential to export directly to renderers with command line options (currently not fully implemented).
15) Developer is actively seeking out, regularly, program enhancements from users, including what export/import formats to support as well as what tools should be added.


Silo weaknesses
1) It still has some bugs in its initial release for some people, mostly with OpenGL redraw on certain system configurations.
2) No mouseover text for tool functionality on buttons.
3) Limited surfacing tools, limited booleans, and some bugs/limited functionality in the array and duplicate tools.
4) A few other bugs with dragging of the mouse outside of the Silo screen under very specific operation conditions as well as some bugs related to the manipulator handles in the orthographic views.
5) Import and export formats are not very clean at the moment.
6) Simpler documentation (which could be a strength), but certainly not as comprehensive as it could be.
7) Dual screen troubles with opening and docking of editor windows, windows get lost.
8) Background images don't stay persistently linked when a file is saved, exited, and loaded again.
9) A few strange bugs related to brush tools after consistent use, hard to nail down, saving the object frequently is important.
10) A bug with inset scale that can cause polygons to disappear and flip some normals.
11) There could be some memory leakage/buildup with prolonged use. At the end of my 12 hour sessions I definitely saw some slowdowns, and the geometry wasn't that dense, or even that much "more" dense than I had originally made it.
12) Some users have had trouble with buttons missing on the interface.
13) MAC is out and supported, but not as clean as the PC version at the moment I think.
14) Partial subdivide was taken out of the program, no word on when/if it's coming back as of late.

Hexagon strengths:

1) Much more comprehensive surfacing tools. Lofting, sweeping, etc.
2) Dynamic geometry.
3) Texture painting, although limited still for sure.
4) A better poly to poly workflow for extrusion with the combination of the ctrl key, and the better planar constraint handles on the manipulator(s).
5) Much more extensive 2D drawing tools, lines, arcs, curves, etc.
6) Better snapping tools.
7) More premade real time viewport preview options.
8) 3D Text tool.
9) More standard UV "mapping" tools.
10) Some decent videos in the documentation, and more comprehensive documentation.
11) More subdivide options for global model tesselation.

Hexagon weaknesses:
1) Still bugs in workflow, including crash bugs.
2) Lower polygon support, at least for me.
3) Very limited UI customization, icons are nice, but not for everyone, and there is no obvious way to change this.
4) Dual screen is not supported at all, at the moment, at least not on my machine.
5) Center seam issues, still, but less than initial release.
6) Less intuitive workflow on "many" tools (constant validate button use on many tools, strange terminology in UI (facet, 1/n, validate, tesselate tool).
7) Difficult to find or understand certain tools such as the ability to lock the subdivision geometry a specific level and delete lower levels, took me hours and a forum post to finally get how to do that simple thing in the dynamic geometry tab.
8) More cumbersone brush size and strength adjustments.
9) Much more cumbersome and less intuitive "smooth/subdivide" methods.
10) Documentation still has poor french to english translation in many areas.
11) Developers seem to go in a "hole" for extended periods, no direct responses to user bugs or inquiries, product "feels" unsupported and potentially dead.
12) No SDK, and no hint or commitment to SDK development.