McDonnell

Hi all I am about to purchase the needed things for an DIY eGPU but first I have a few things I would like to ask. I have the following laptops: Thinkpad T61, T500 and T410 all with integrated graphics. I am guessing my best bet would be to use the eGPU with the T410 due to it has an I7 cpu. However It would be great if I could also use it on my T500, would that be possible? I have been looking at the PE4L v2.1b and PE4H v2.4a and I am really not sure which one I should by? The PE4H is around 30 USD more expensive than the PE4L. Your help is much appreciated!