Not a dumb question at all. This is explained above pretty well pretty well but I'll add in my two cents since I've used both tools.
I've used the Block with great success; in my opinion it (when used in conjunction with a good quality drill press) is a one of the key reason I've been able to enjoy relatively good success in league racing with the handful of cars I've built to date.
It seems logical that there would be many more people using and espousing the merits of the Pro Body Tool or Jig simply because it does not require near the capital outlay required to acquire a Block/drill press combination; it (the Pro Body Tool) is pretty inexpensive and readily offers the novice builder the ability to achieve significantly improved alignment versus simply inserting axles into the normal grooves/slots on a BSA pinewood block.
The Pro Body Tool (and I'd imagine this holds true for the Jig as well although I have not used it) is a great tool to use for the vast majority of folks who are racing at the Cub Scout Pack and perhaps even District and Council level, especially if the car is not running any rear camber. I purchased a Pro Body Tool last winter and I attribute my son's ability to take first place in his very first Pack race to the improved alignment this tool allowed us to achieve (running zero camber).
When we advanced to our District race, I knew we'd be facing much stiffer competition (~3800 cars feed into our District). Having learned much more about advanced building techniques and the physics involved, we decided we'd experiment with running negative camber on our rear wheels. Not being confident that I could achieve optimal alignment via bending our rear axles, I tried to drill cambered holes (so the angled holes imparted the camber to the axle/wheel rather than a bent axle). Drilling accurately cambered holes using the Pro Body Tool, however, posed a challenge for us, because we had to remove the tool from the block of wood in order to shim the side opposite the side I was drilling, prior to drilling the second side of the block, and I was never able to reposition the Pro Body Tool in
exactly the same fashion so as to allow my holes to be perfectly aligned. After several attempts to drill "perfect" holes I was frustrated beyond belief... the car would crab sideways down the track, or the wheels would fight each other, etc... we finally acheived decent alignment after hours of tweaking via bending the axles slightly and rotating them until we found the sweet spot. That car ended up placing third in our District, so we were pretty pleased with the results.
But once again, we knew in advancing to our Council race that we'd be facing 10 times the competition (~38,000 cars supposedly compete to qualify for our Council race), and we knew we'd have to step up our game in order to be competitive. I also felt pretty comfortable with my knowledge of body design, weighting, wheel and axle prep, etc., but realized that alignment was our achilles heel.
It was at this time when I first read about the Block; the primary benefit I saw in using it was that I wouldn't have to remove the "Block" from my wood block when drilling cambered holes. Having struggled with achieving optimal alignment when running negative camber on the rears, I broke down and bought a drill press and a Block. I didn't fully understand the benefits the block brought to the table, but it seemed as if some very fast builders were using it so I coughed up the money for what I hoped would prove to be a good system for drilling accurate holes.
It is my opinion that this tool really helped us to raise the bar on our cars performance (we ended up placing 3rd in the Council). For league racing purposes, I can now drill a set of holes
in about five minutes and have close to perfect alignment with zero tweaking (assuming I've got straight axles and bores etc.). With accurately drilled holes and a properly weighted body (i.e. .5" - .75" or so COM), I can literally slap in a set of
straight axles and decent (lathed tread) wheels and have a car that I am confident would be
very competitive in any Cub Scout District or Council in the U.S.
Both the Pro Body Tool and the Block are good tools for their intended use. In my opinion, drilling holes with the Pro Body tool (use a pin vice versus a power drill so you don't drill out the holes... I found this out the hard way) offers a huge improvement over simply using the slots found in the BSA block, and it is very affordable for the typical Cub Scout builder. It helped us to make the very first car we ever built a Pack winner.
If a builder wants to take their cars to the next level (i.e. league racing or a very competitive Pack/District/Council) and can afford a drill press and a Block (or they already own a drill press), the Block offers a very simple way of drilling nearly perfectly aligned holes very quickly every time, and allows you to experiment with varying degrees of camber by using different sized drill bits to "shim" it off the drill press table. Another benefit of the block (versus simply drilling holes with a drill press and no other tool) is that it compensates for a BSA block that may not have sides that are cut
perfectly parallel to each other (this one is hard to explain and I've been way too wordy already, so you'll just have to trust me on this one...
).
I've been using the Block to drill the holes for my proxy racing cars, and I am very pleased with the results I have been able to achieve.
Neither tool will guarantee you a blazing fast car (as alignment is only one aspect of what comprises a fast car), but there is no substitute for good alignment, it's one of the most important variables in building a very fast car (in my opinion for what it's worth).
Steve B.
). 
8-)PREACH ON BROTHER! I HAVE SEEN A LOT OF TOP RACERS SHUT OUT OF OTHER FORUMS FOR JUST TRYING TO ANSWER THE BIG QUESTION "WHAT WORKS BEST FOR YOU?" IT MAKES NO SENCE TO ME, WHY THERE IS SUCH TENSION WHEN IT COMES TO TALKING ABOUT ALL THE TOOLS OUT THERE. DO THEY NOT WANT THEIR KIDS TO BE THE BEST THEY CAN BE? ANYWAY I AM GLAD I HAVE FOUND A FREE SPEAKING FORUM THAT'S GOAL IS TO HELP EVERYONE SUCCEED!! GOOD LUCK IN '09, I LOOK FORWARD TO RACING WITH YOU! 
