In short (pun intended)
They are stronger being shorter.
We'v done a bunch of broadhead testing on buffalo the last few years and found the Shorter - Smaller heads to be a lot more durable. Considerably less prone to tip curl.
The structural integrity deceases with length, and the increase in leverage in the long heads compared to the shorter heads, means they are simply much easier to bend which =(tip curl - snapping and adapter's bending)
"take a 30" arrow shaft and a 10" arrow shaft and see which bends the easiest"
The Guys at VPA recognized this before I could show it in testing, and already moved to making the Bigger heads "shorter". And now The original 300gr 2blade has been reduced to the length of the 250gr 2blade, the extra weight was made up by increasing blade thinness. Thank you VPA!
One concern and Idea that is common is that the Longer head penetrates much better then a shorter head due to its reduced angle and the difference in its mechanical advantage. However, this is Not the case in testing, there is at best a "marginal" increase in penetration at the best of times, BUT *here is the table turner*, that is only the case if the head does not bend "tip curl" you go from "marginal penetration gain to hugely reduce penetration" Enough to cost more then a few friends and clients there buffalo, with the longer heads on the market.
The fact is the strength gain and reduction of tip curl in the shorter heads, outweighs the marginal penetration gain a longer head may offer when it stays strait.
So use with Confidence Shane, they are bomb proof.
Iv been using the Tiny VPA 150gr 2blades on hogs out of the longbow and you should see those things Zip through big boars.
Good luck.