That is the question!
I took my Tech License test after going through the multiple guess tests on Eham.com I am not sure that a lot of potential hams understand that not only is every possible question available on the practice tests, but every answer is there, verbatim, too. If you play the practice test game, you can memorize every question in the test pools with ease.
Manufacturing APRS transmitters, I guess you would expect me to be biased, and I am. But I am also a Major in the Civil Air Patrol and an (inactive due to health) Ground Team Leader. ( The guy who comes to find your azz when you are upside down in the trees with Avgas running down your neck) Great news is that the new generation of ELT's are start of the art awesome; Bad news is they often don't survive a crash ( or at least with a valid GPS position available) This means CAP or other group has to find you by blind luck. An APRS track will give us your course, speed, and last known position even if it too, does not survive the crash. Its a big world when you are looking for a little airplane, and any intelligence we have to know where to start looking is a major kick start. The coverage is not 100%, but at altitude, it starts reaching 100% pretty fast. Altitude is time.
Whether you use my transmitters ( Which of course, is the wisest thing to do ) or anyone other one, the real limitation is usually the antenna. If you use a Vertical belly whip, your unit will outperform the cross polarized wing tip antenna dramatically, but I understand your reluctance to drill holes in your ship. Pretty cheap insurance.
( The Micro-Trak guy from Byonics)