Yes, especially if you live in a place like I do, the PVC/burial thing is tops. No one can steal what they don't even know to look for (OPSEC!). Yet you can find it later with a metal detector, even if the vegetation has changed a bit. You wouldn't do this in some dense suburbia, since you'd be noticed out there with your shovel at one end or the other of the process.
Now, I have some other options too - I have a few buildings here, and have had the experience of being full-searched (for drugs), and found out where they do and don't look. So there's a bit of "heavy metal" of various sorts here and there in places no one looks (think behind junk in a storage building, inside walls...attic..behind cobwebs so it looks like no one's touched it in a long time (the actual case). And those cobwebs or mouse poop let me know it's still there without having to check, a variant on the old trade-craft of hanging a hair across a door-jamb or dresser drawer to see if it's been opened since.
Interestingly, I had this same idea (I believe it was discussed here somewhat earlier too). I've got stock of the pipe etc, but I didn't want to get into my lab prototyping stuff, so I went to Lowes right about when the fear about Obama and guns had made it hard to get either guns (prices sky high) or ammo, to buy some more to make a few of these. Guess what? They were out of stock, totally.
(I had to go to a local but not well known PVC pipe wholesaler to get mine.)
So I ask the Lowes floor-walker guy what's up. He sez that for "some strange reason" a ton of people had been in there the last few days buying it all up, and they hadn't gotten restocked yet. He thought it a little strange that people were buying pipes, caps, glue - and no other fittings, like a plumber would be doing.
It's nice to know you've got company.
The big safe thing just doesn't get it for me, personally. I keep a few guns around where they don't show, but I know where they are - ready (and which are loaded - I don't have kids to worry about). And a tiny amount of PMs, kind of a bug-out amount, an amount I could lose and it not be the end of the world (but which might satisfy a thief such that they stopped looking). Lots of people around here have those big safes for guns, some bolted, some not. There have been attempts to steal them - it's advertising you've got something that needs a safe, after all.
They do tend to work against the stupid...there was a case 3 years ago where someone couldn't crack the safe (obviously they didn't read the MIT paper that shows how to do it easily) - so they tried to steal the entire thing. It was found in the front yard - with an *arm* under it...and a blood trail.
Weight and gravity appear to beat stupid.
On the other hand, a safe is no good against the .gov, or what we in the security biz used to call "rubber hose crypto". You think you wouldn't give up the combo under torture, or threat of the death of your family? Get real.