You are probably fine with either one of those. The one thing that may make a difference is the fact that the PCI one would be inside the case which may interfere with the signal. That is just a theory though, and it may not interfere at all. As long as you get one with decent length antennas you will be fine. I got an adapter in the past that was the size of a thumb drive and it was terrible.
I would just get the cheaper one and if you are not satisfied, return it within 30 days and get the other.