Clutch rear derailleur vs chain tensioner / guide I've got a 1x10 set up. Sometimes I have a problem with the chain falling off at the front. I've been reading that a clutch mech will help to prevent this. 

My mech is Deore long cage without clutch. What is the dis/advantages of a clutch mech vs a chain tensioner / chain guide? 

Bike is 2006 Specialized Rockhopper Pro. Chain is correct for chainring. Its not worn, nor the chainring etc. Chain line looks fine, but maybe this could be tweaked slightly.
"Once or twice per ride" - that is way beyond what I would consider only. That would destroy my confidence in the bike and ruin any enjoyment I got from riding. 

A new dérailleur might help, but might not. There are other things I would look into first, PeteH in his comment is correct - the number of drops you are suffering is an indication something is very 'not right'. If a new Clutch dérailleur appears to fix it, its is probably just masking the problem. Chain guides hide all sorts of evils, but are a practical option that will work. 

Shimano 1x10 was not an out of the box set up, what was the original setup and what has been replaced with what? 

What chain ring are you running, is it damaged at all?. If you are running a normal 3x or 2x chain ring, a chain-ring for a single will help, especially a narrow/wide. 

What is the chain line like. When you drop the chain, is it in normally in a particular range of gears

Along the same lines - is the chain length correct. As its a long cage dérailleur you have a lot of scope for too much chain. 

How worn is the dérailleur - its more likely a new one will help of its been used a lot. 

With so many unanswered questions,  I would consider a new dérailleur if the other is well used, but would focus on chain (how old, does it need replacing and length) chain line and chain ring first. If these are all good (and the chain ring is dedicated for single, ideally narrow/wide), the choice is a new dérailleur which might work, a a chain guide while will work.