There is no comparison. With an IR filter you will end up using slow shutter speeds as not only do you keep the cameras IR filter but you add another filter to keep out the visible spectrum. You may end up with shutter speeds of 15 seconds or so - needing a tripod and moving objects will of course blurr.
Taking the IR filter out of the camera is a good option - you will still need to buy an IR filter to cut out the visible spetrum
Better still buy a converted camera on Ebay - I have a colour enhanced converted camera (an Olympus E410 slr that I got on Ebay for 500 USD. had to buy a lens for it).
You can get stronger effects then by putting a polraising filter on it and end up with the choice of strong monochrome IR images or coloured IR images. The colours can bes swtiched around by channel swapping in PP.