Well, gee, I'm not convinced. So I tested it a little.

I went looking for example SVG files, and I found the New Zealand flag on a Wikipedia like site.

Inkscape (0.45, version of 1 year old) simply doesn't show the stars.

SVG is the native format of Inkscape. So, what to think of it? I can't say I've ever tried to do anything with Inkscape that it didn't have some kind of trouble with.

ImageMagick's convert performs slightly better, as it shows the top star. But only that one.

p.s. the output file sizes from ImageMagick:

• JPEG: 71kB
• PNG: 19kB
• GIF: 10kB
• Original SVG: 3kB

showing just how inappropriate JPEG is.

p.p.s. your Inkscape command line simply doesn't work for me.

update I got Inkscape to behave, on Windows. Here's what I did:

• I upgraded to the latest version, 0.46. That one does show all the stars appropriately.
• I made a copy of inkscape.exe to inkscape-console.exe. With exetype (comes with ActivePerl for Windows) I set its exetype to "console". That way, I can get diagnostic output from the console.
• It turns out that Inkscape takes relative paths to be relative to the executable! not to your current directory. When I used an absolute path for the SVG file, and just a file name for the PNG file, it placed the PNG file in Inkscape's own directory. Conclusion: always use absolute paths for input and output files, at least on Windows.

p.p.p.s. Inkscape's PNG file is 25kB, as opposed to ImageMagick's 19kB. And I find it's relatively fast. I doesn't appear to support export to the other bitmap formats.