Made a strange discovery today

I normally play a premium ball (z star or tour D) but found a TM burner and Titleist nxt extreme on the course today.  I was just practicing on my own so I was hitting a few balls at a time.  I discovered that the premium and 2 piece balls hit the same distance off my driver but the 2 piece balls were hitting up to 20 yards longer with my mid irons.  20 YARDS!!!!  I was hitting 2 z-stars against the TM and NXT (obviously, I only counted the balls which were hit consistently).  They were 20 yards longer with my 7 and 8 iron and 10-15 longer with my 9 and PW.  Has anybody else experienced this?  Why is there no difference in distance with the balls off the driver?

I am seriously considering a switch to one of these 2 piece balls, the only down side to them is the roll out you get on pitches, but I could quickly adjust to that I think.

temperature where you played? how'd they spin?

It was about 9*F today, the z-stars stopped within a few feet and the nxt rolled out maybe 10 feet more.  I can understand the 2 piece balls going further but not sooo much further, and why not with the driver too?  I am going to do some more testing tomorrow.

if it's cold, you may not be getting the better performance balls to perform as it would if it were say, 75* out...i know when it's colder i play better with 2 piece balls, in terms of distance that is. when it's warm i prefer the 4 peice balls.

I'm sure the ball manufacturers' websites will go into great detail on this but, as I understand it, the premium multi-piece balls are designed to produce low spin at high velocities (drivers) and high spin at lower velocities (irons).  The two-piece "distance" balls are designed for low spin all the time.  That's why the iron shots would go farther, but probably not stop nearly as fast. The driver distances are relatively the same with either ball.