Okay, I'm not Robbo, but I'll try to explain.
The reason a stock Angel is perceived as being more accurate than a stock Tipmann is simple: (for this example we'll assume both markers have the same air source)
First of all, the stock barrel that comes with the Angel is a pretty nice one, two stage bore, nice and smooth finish, the works. The barrel that you get with a stock Tipmann is, compared to the infinity barrel on the Angel, just a piece of metal with a hole in it. It isn't nearly as well finished as that of the Angel, which results in all kinds of unpredictable frictions causing all kinds of spinning on the ball, which in turn results in a ball going god knows where.
To negate this advantage, let's assume we put the same barrels on the two markers. It now no longer is a contest of marker/barrel versus marker/barrel, but just marker versus marker.
What will make the Tipmann lose in this situation is consistency. The shot to shot consistency, measured in fps, is nowhere near as good on the Tipmann,as it is on the Angel. This results in one ball coming out at, say, 285 fps, the next one at 274. This means that one ball will fly further than the other one, meaning it has a different trajectory. In turn making it look like the gun is way inaccurate, because it's balls don't form nice and tight groups. The Angel will make tighter groupings, because the difference in fps between shots is far smaller, thereby causing less difference in trajectory.
In all honesty, it is probably possible to make a Tipmann just as accurate (although we should really use the word consistent), but it would involve getting a grade A barrel, a superduper air source (Angel A.I.R. or Armageddon or suchlike) and a lot of regulators and aftermarket upgrades. All this results in getting an air source that is two to three times as expensive as the marker, and when you count in all the upgrades needed, you'll be in a price range not too far removed from that of an Angel. So it would be a bit silly, because you'll spend more or less the same amount, and yes, you'll have two equal markers in consistency, but the Angel will beat the Tipmann hands down in rate of fire, looks (though that's just an opinion ofcourse), and ergonomics (ease of servicing the marker, etc.)
Hope this explained it somewhat.
