I am debating on getting the Xcal 2 but don't know whether I should order it from MPH and get an off the shelf tune or take it to performance evolution, a local guy and get him to tune it on the street?
A lot of that is old style thinking - Back when everyone did chips, this was entriely correct - nowadays you can get VERY close to dynotune quality via mail order as long as you have the right equipment and are willing to work at it.
You need an XCal 2, a laptop and a wideband that'll also log MAF volts or RPM or can be interfaced to the Xcal 2. Widebands have come down in price and are no longer unaffordable. You log what's necessary with the Xcal and the wideband on the laptop and email the tuner the logs. Then you get updated tunes from the tuner. This goes on until the tune is correct. Lots cheaper than a dynotune, plus you have the satisfaction knowing you participated in the tuning process. WOT runs can get hairy on the street, so we always tell people to have another person driving, and to obey all speed limits - or better still, do it at the track. One negative thing is you don't get dyno numbers.
I've done TONS of cars this way with great results. Cars from all over the USA, Europe, South America and the middle east - all over. We do enough cars on the dyno to know where the best fueling and timing is for 90% of the cars with the same combo, so once the tune is dialed in via this process, you probably are only giving up a small amount of power, if any. Plus no dyno - Mustang Dyno or any other will load the car like the street or track will. You only have to find a tuner who has the time and desire to follow through with you and keep at it, and gets back to you fairly quickly.
Don
a SCT tune is going to be much better than the old Superchips. ultimately a custom tune is the best, but probably not worth going to a tuner for unless he gives you an Xcal2+ in the deal.