Two things to keep in mind, primary size and length, typically a 1 5/8 primary will make more high end power and a longer primary will too, 1 3/4 and a short tube will make best at low rpm's, just from what i'v seen.

 

Im pretty happy with my macs, I was originally going to swap to long tubes when i do heads/cam this winter, but I think I am going to stick with these puppies, pretty good power, great plug access, and no ground clearance issues!
Brandon

 

Flip flop that statement and you'll be correct.

Narrow long primaries make low end power.

Wide short primaries make top end power.

 

My MACs are on a ported head/CC305 combo and are working great. They have all the good qualities you listed, plus...They're easier to install.

Frank

 

Car Craft did a dyno test a few years back comparing shorties to 1 5/8 lontubes on a mild small block. While the longtubes did produce about 15hp more on the top end, the shorties pounded out way more tourque on the low end (up nearly 25 ft lbs around 3k). My own experience shows the same. Swaped longtubes for shorties because of ground clearance issues. Gained low end but lost top end.

Right now I'm in the process of installing AS&M headers. Bought them because they are the best balance between power, ground clearance and ease of install.

 

Mitigating factors can cause the experience you've had, but in general, longer tubes make more torque. Thats not opinion thats science.