Hazards on endurance rides related to horse size

[keithr@nocdc.bc.ca (Ann Hatfield)]

In my on-going friendly arguements with a long-distance trail riding friend
the subject of the 'best height for trail horses" comes up frequently.  He
(and me too when I'm back up there visiting-God's country-the Canadian
rockies) rides trails that often have logs across them,  steep banks, mud
holes, bogs, deep creeks, rivers, and other hazards.  His contention is
that a large (15:3-17 hand) horse is faster at a walk and trot and much
better over this type of terrain.  Sadly, I have to agree when it comes to
logs across the trail and some of the banks his French Trotter/Saddlebred
16:2 gelding breezes over.  But, am I likely to encounter much of this in
endurance races as such?  

The one and only I have ridden in was in rough country (the Rockies) and
had several deep fords and a truly horse-eating mud hole-thank goodness I
was early to it, before it got really churned up -so soft that a couple of
horses nearly were very nearly mired and one unwise rider who dismounted in
the middle of it darn near disappeared!

I have a green 14:3 gelding who will be hard pressed to keep up to Daniel's
gelding in the blowdown but whom I think will blow the socks off the
bigger, bulkier horse over a long ride and is neat and nippy under the
branches that nearly decapitate riders way up there!

Do many (any) rides have hazards like the above and so is a leggier horse
an advantage in this way?

Ann