The other consideration is that an audio interface will typically endure through at least a couple of computer changes, so having an external unit based on USB, especially if you are not using anywhere near USB’s bandwidth, may be more sensible.
On the PC side, PCIe will probably endure for a few more years, but Apple has dropped internal PCIe on the new Mac Pro, and as UAD2 Solo, Duo and Quad users have discovered on the new Mac Pro with external Thunderbolt PCIe bays, newer PCIe systems may not be compatible with older cards.