I have in the past and continue to recommend C&L MAF's for SC's. The reason for this is that they are simple and they do the job. For many SC owners simplicity is important and for this convenience you are going to pay a bit of a premium. There is nothing wrong with the MAC sample tubes, but I agree the shipping is a bit high for something that can be mailed cross country with 2 day service for around $2.50. Nothing I can do about that other than to start stocking MAC parts and then charge actual shipping which I may do if there really is call for it.
C&L MAF's still represent value and with all the people upgrading to slot MAF's these days, the used market is very good. They don't wear out, so don't write off the used market as a good source for these parts. Sample tubes are also available as many people bought them and upgraded over the years. Put a post in the wanted section if you need a particular color tube. Best bet is that if you intend to upgrade significantly in the future, look for a MAF that already has the size and calibration you ultimately want, and then sell your existing one to someone with lesser goals. Chances are the upgrade won't really cost you anything.
Regarding other comments above, it is true that there are other options but unfortunately not all the information you see above is entirely accurate. You cannot just use ANY MAF if you purchase tuning software or get a custom chip from me. All MAF's have a RANGE of operation and if you exceed the range of operation for a particular MAF (MAF and calibration combo), then the game is over and you can't do anything about it. Think about it in terms of HP levels, or blower OD levels, moreso than injector size or calibration. The two are inextricably connected, but one does not determine the other. They both support HP levels (or more accurately airflow levels) and you cannot cheat either one.
For a physical plug and play MAF that will support more than stock HP levels, you are limited to C&L and Pro M calibrated MAF's. C&L offers a convenient calibration chart to help you understand which one you will need in most cases, but when dealing with Pro M MAF's this is not the case. Pro M MAF's will physically plug in, but they are typically calibrated for a Mustang and are notorious for leaning out the AFR at higher rpm's and load values unless you have a tune to match them. Therefore a Pro M MAF is typically not a true plug and play option. They are also more expensive. The plus is that Pro M will service them for you and even change the calibration if you want. The minus is that the cost of that service is worse highway robbery than the MAC sample tubes.
For other non plug and play options you get into MAF's that were originally designed for an EEC V or OBDII application such as the Cobra or Lightning. These MAF's are larger (4" outlet) and require adapters on both sides to fit an SC. They also require rewiring the plug which means that you are now taking on more responsibility for the proper running of your engine. I've seen many botched wiring attempts and have had to deal with the problems that follow. I am also continually amazed at the physically botched adaptations, with blockages and turbulence causing all sorts of tuning issues. So while this is not a bad option, it means you have to do the conversion right and you have to have a tune to go with it. The MAF's themselves are good quality and will support up to 350-400rwhp depending on how greedy your particular engine happens to be.
The slot MAF is a much newer configuration of sensor that is used universally on all new Fords. This was a smart move on Ford's part because they now have to stock only one part for all their cars. It also helps us because it standardizes things a bit. However, there are always drawbacks. First, you will absolutely require tuning to use this MAF. Second, the range of this MAF varies greatly because just like the old C&L sample tube concept, the size of your tube dictates the range of the sensor. A stock Ford sensor in a 3" tube will have about the same range as a stock MAF. The sensors are also very sensitive to orientation and installation. This means again that your results will vary based on where and how you install the sensor. Third, you will now be responsible not only for the wiring of the sensor, but also the mounting of it. You'll need to buy a flange and weld it into a piece of tubing. And finally, not all slot MAF sensors are the same. Because an OE slot MAF will max out in even a 4.5" tube at around 500rwhp, and because many people like to run blow through in a 3" tube, SCT and HPX as well as others, have taken to recalibrating the slot MAF's and reselling them. These sensors are not calibrated to any particular HP level or injector size, but they have greatly extended dynamic range and require their own tuning parameters. Just an FYI that not all slot MAF's are the same.
If none of that is particularly daunting to you, then by all means go for it. The sensors work well and the whole thing offers more flexibility of installation. But if you are scratching your head at any of this, or are the type to throw in the towel when the thing doesn't start and run perfectly on the first try, or if you are the type to throw in the towel because you ended up having to buy a new flange and start over cause you messed something up, then don't even bother thinking about a slot MAF. Know your limitations before jumping in because the car won't run without a properly calibrated (meaning between the sensor itself and the table in the EEC program) MAF. I can predict the output of a C&L MAF pretty well when it is installed in normal configurations, but when you fab up a slot MAF on your own, all bets are off. Don't count on a mail order chip being able to accurately match the output curve of your now custom MAF.
Hope that helps some.