The sampling mode only affects WebGL, which is not supported in IE9, so it's impossible it has any effect on IE! It must be random, or dependent on something else, and you've accidentally spotted a pattern.
It's hard to know why IE9 is laggy - if your game is particularly intense in graphics, IE9's renderer is much slower than Chrome and Firefox's because it doesn't support WebGL. Try turning off WebGL and see if the other browsers are equally laggy. If so, you should just recommend your users use a WebGL-supporting browser.