i looked at trailers for years before i bought the one i have now
you will see alot of shite out there second hand , and most of them need a rebuild
new is good if you got the cash , and tilt beds are the bollox, i havnt got the cash so ai bought a good second hand unit that needed a bit of alteration for my car .
if your thinking of putting the sierra on it m8 , then you will need a massive trailer, more than likeley a 16' x 6' deck, this was part of the problem i had trying to find one
mine is now 17' x 6'8" so is just mint !! though i had to rewire it, and mount the ramps to the back of it , and extend them to suit my car due to loading angles

but its now done a fair few miles with no worries and is a heavy duty unit!!
also you will need to watch out for towing weights to keep it legal !!
mark