Re: form submission differences?
A bigger question is why you seem to think that JavaScript validation would prevent you from using <input type="submit" />. JavaScript form validation (a mere user convenience) should be called from the form's onsubmit event, returning false on failure and true otherwise, and should be backed up by server-side (true) validation. Your page should work just as well with JavaScript disabled as it does with everything working as planned.
“Beware of bugs in the above code; I have only proved it correct, not tried it.” --Donald Knuth
"It was as if its architects were given a perfectly good hammer and gleefully replied, 'neat! With this hammer, we can build a tool that can pound in nails.'" -- Alex Papadimoulis (on TheDailyWTF.com)