As stated, it depends on how you intend to use it. An SN-95 makes for a more comfy DD, whereas a notch is an awesome foundation for a weekend beast.
Both cars have their merits and drawbacks.
As stated, the SN-95 has better brakes, 5-lugs (more wheel choices), they're quieter, and if you get a '94-95 GT, then pretty much any engine upgrade that will work on a Fox will bolt right in there, as well. However, the trade-off is that they're heavier, not everyone's a fan of the looks, and their cat-back exhaust setups are different than a Fox (might affect your selection).
A Fox notch will be one of the lightest Mustangs you can find. The SN95 brakes, spindles, and axles will bolt right on, although doing so involves added cost and installation time. They usually have a ton more squeaks/rattles than any SN95, a fair amount of body flex, and they tend to be rusted all to heck in most parts of the country. Probably not the best choice for a DD as far as overall comfort, but I DD'ed one for a couple of years year-round here in Arizona with no A/C and a half-stripped interior - no problems.