Rectum creek caps do suck! I recently had the opportunity to compare the next generation Aadland caps along side the Vortex defender caps. Both work, and both are robust, backed by killer warranty.
If on a budget and you have a smidge more scope clearance, the Vortex defenders are a great option. The major con for me with the defenders is that they only have tabs to open the covers, and they are thicker. The Vortex have a more flexible rubber ring that allows these to fit a given range for its size, combined with a stiffer rubber compound around the flip lid workings. The defenders also have built in stops, so they do not open all the way upon gentle opening - at least the objective cover does this - I suppose to work with the new dope inserts that Vortex has
If you have less clearance (scope bell to barrel) the Aadland caps still rule the roost. The next generation version of Aadland's now come with a non obtrusive pinch feature that allows you to further snug down your cap using a small slit cut into the rear of the cap and small bolt/nut combo built in. These tank built caps are going nowhere! On the plus side, the ocular caps still have the push lever that activates the cap. I really like this feature over the Defenders. Also the Aadlands are overall slimmer in diameter.
All in all, either brand should work for a person over the long haul and not break from cold or just using them.