The OEM Jensen/BAT PIOs in my VK75SE are surpassed in all respects by V-Cap TFTF. I don't know if those Jensens are copper or alum. I have not compared Mundorf directly to Jensen PIO.
I think you'll find that PIOs in general have less clarity than teflon and other good film coupling caps. (Mundorf Silver/Gold are not oil caps.) If you want to experiment with a nice oil cap on the cheap, consider russian K40Y-9s on ebay. Knowledgeable posters at AA believe these to be the best of the PIOs. I have a bunch that I haven't yet installed. They appear to be built to a very high standard.