The general rule of thumb for what to spend money on is this: if it is a hand tool with moving parts or that will be used in spots with clearance issues, the tool truck tools are likely worth the money. If neither of those two criterion exist, it probably isn't. Frequency of use is another important criterion. If you will only use a certain tool a couple of times a year, it probably won't pay to invest a lot of money into it. The final factor is that sometimes innovative tools are only available through the tool trucks (meaning the Chinese haven't figured out how to copy it yet).
I just wanted to highlight a few of the tools that I believe are worth spending in order to get quality. (Disclaimer: I have bought exactly three tools off the truck. I use either Ebay or Craigslist to buy spendy tools.) Our shop is serviced only by the Mac and Snap-on trucks, and the Snap-on Customer service is lacking, so my tool collection reflects that. Some shops have a good Matco or SK or Cornwell guys, so that is a consideration when you are buying tools. If your shop gets good customer service and prompt warranty from one or more of those companies, that can make one tool stand out a little more than the others.
As an aircraft mechanic, one of your most used tool will be your 1/4" drive ratchet. I have a decent collection of them and I have borrowed a lot more. I can tell you that hands down my favorite ratchet is the Mac tools MR4C. Nobody else that I have found makes one that is as small, low profile, fine toothed, and tough. This is the most common ratchet in our shop. There are six of them floating around, with very good reason. If you can buy it with the student discount it is only around $26, but even at $52, this is a must have tool. There are certainly other good options, but I am partial to the 72 tooth design. It seems to have a smoother action, and it can be invaluable in tight areas.
Another tool that is worth spending for is a good set of 1/4" drive flex sockets. The cheap ones do not last or work as well, and most of them are six point. You will want twelve point in case you work on turbines. The Mac set (which I own) is good quality and very low profile, but sometimes it will not work for cylinder base nuts on reciprocating engines because the socket is not deep enough, so several guys have the Snap-on 7/16" and 1/2" because they are longer and deeper. In my experience, however, the low clearance that the Mac set provides is more important.
|Top to Bottom: Harbor Freight, Mac, Snap-On|
|Mac and Snap-On wrenches with 15 degree end (Mac) aligned|
with 30 degree end (Snap-On)
|Top to bottom: New Snap-On, Caterpillar, old Snap-On|
|The newer Snap-On and Caterpillar wrenches are identical,|
but the older Snap-On is slightly smaller headed. I am
guessing that they thickened it up to save themselves
some money on warranties.
These are just a few of the most important tools that will cost you to skimp on. There are many others, but I think that these are the most important. Watch for my breakdown of what tools are not worth buying off the truck.