What is the best way to do onload Script execution?

prototype

// onLoad Syntax with calling jQuery in "Person" 
  jQuery(function() { 
  var cheight=$("#content").height();
  var nheight=$("#navbar").height();  
  if (cheight>nheight) {
    $("#navbar").height(cheight);
    }
});

// same as above, more terse, we assume jQuery  loaded
$(function() {
    $('#topslider').do_stuff...;
});                                                  

// use this with Prototype
document.observe("dom:loaded", function() {
  Site.adjustNavbar(); 
});