The Mobil 1 is a great filter. You can feel how much heavier it is when you pick it up and I have seen them cut apart and know that they are a quality product. However the big difference between extreme quality filters like the Mobil, and the less expensive filter such as the Delco is not in their ability to filter out debris (the micron size of the particles are all about the same since this is the specification they must meet to be approved for use by the manufacturers during the warranty period) but in the amount of "crud" (technical term) that they can hold before going into by-pass mode. That said, if you change your oil and filter regularly the filter will never approach the limits of the amount of crud it can hold, so you can use a less expensive filter without fear of damaging your engine. You still want to stay with a known quality brand, but they are available for about $4 rather than the $12 for the Mobil 1. I have also heard that the Delco filters seem to do a better job of keeping oil in the engine overnight (anti-drainback valve) so there is less of the dreaded knock on cold startup. I have used both in my truck, and found that the oil pressure does seem to come up quicker with the Delco filter.
Hope that helps.