Pre gunpowder or post?
I’m mostly interested in the battlefield. It’s pretty much a given that the life of an army grunt is far better outside of combat nowadays.
In an actual battle though, would it be better to be say, in the middle ages with swords, spears and arrows or in WW2 with bullets?
There is no better time to be an infantry grunt than now, for the simple reason that up until the Vietnam War, more or less, soldiers routinely dropped dead of disease and infection more than wounds. With the advent of helicopter evacuation in Vietnam, American soldiers could be taken at speed to army hospitals that effectively evolved into modern “trauma centers”. The wider availability of antibiotics and other drugs greatly reduces the chances of dying of disease.
There is a downside to modern combat, with night-vision goggles and satellite technology and rifles and whatnot, meaning you can be targetted day or night from a great distance, but the enemy has the same limitation, so it mostly evens out. If anything, modern combat has become more intense but of shorter duration. Compare that to a Roman soldier who would march away from his home for years at a time and was lucky if he came back.
Never.
.
I’ll second Bryan (at least when it comes to “western” militaries). Infantrymen today are better trained - considering how few they are compared to the rest of the military, they’re practically specialists - and better protected than they’ve ever been; modern infantry tactics stress survivability; unlike in the past, having a brain is often an asset; and modern officers at least try to care whether or not their troops come home alive.
Alessan, former grunt.
However, combat has become far, far more lethal than it ever was. Chances are if you started either of the World Wars as a combat infantryman, you didn’t survive it (for example, the U.S. 29th Infantry Division replaced its numbers almost twice over in ten months after hitting the beaches at Normandy).
If I had to guess, I’d say that being a Roman legionaire was a fairly safe bet. Because they were so well drilled, the Roman legions rarely lost (although when they did, they sometimes died almost to a man–see Crassus), and most of the fighting was taken up by the first few lines in the formation, while the rear ranks used shields to afford some protection from missile fire. Disease seems to be less prevalent than it was in the Middle Ages, and despite the fairly temperate climate in which they often fought, winter campaigning was rare. It was not uncommon for the rear ranks of a legion to be manned by soldiers with twenty-five years’ experience. They even had a fairly decent retirement package, eventually.
Perhaps that’s why they were so disciplined and stoic…
WTF? The penalty for desertion was dismissal?
Armistice Day.
Okay - most of the Roman military stuff sounds pretty unpleasant (like everyday life in ancient Rome was such a bowl of cherres, but I digress) - but whats with being forced to eat barley instead of wheat?
The best time is peace time. I imagine it was pretty good to be in the American Army from 1946-1950. Not only peace, but millions of desperately poor beautiful women all over the world who would sleep with you for a chocolate bar. 
No, the penalty for desertion was death.
I’ll note that the OP asked for a time, not a time and place. Yes, the Roman army was pretty good, relatively speaking… But would you want to be one of the Visigoth infantry, during Roman times?
Those Roman punishments aren’t all that extraordinary, by the way. Any military organization at any point in history will have harsh discipline. And desertion in combat and in peacetime are two entirely different things: In the former case, you’re putting your entire unit at considerable risk, but in the latter, you’re mostly just saying that you don’t want to collect your pension.
All in all, though, I think that right now (or at least, some time after the Geneva Accords) is probably as good as it gets, for a grunt. In the Gulf War, for instance, the U. S. suffered what, a few dozen casualties? I don’t think that there’s any other war in history which is comparable. And while the Iraqi troops in that conflict had it somewhat worse, they were at least guaranteed humane treatment if captured or surrendered. The only major downside to modern warfare is weapons of mass destruction, but soldiers aren’t much more likely than civilians to be targetted by those.
Absolutely. British soldiers in the 1800s faced hanging, shooting and flogging (up to 1,500 strokes, until public outcry over the number of deaths spurred legal limits) for a range of offences.
right, which is why being in the infantry pretty much sucked right up until the 20th century (by which time such punishments gradually faded away) and didn’t start getting relatively survivable until modern medicine and antibiotic drugs reduced the rates of lethal infection.
I completely agree. Perhaps combat is more dangerous (in terms of the lethality of weapons), but peacetime is safer and when wounded in combat I imagine the chances of survival are a lot greater since the start of the 20th century.