No person acting in their own interest would willingly face trial in a US court, unless they had millions of dollars to spend on lawyers. The way our courts work, acquittals are expensive and actively discouraged, and there is almost no chance of jury nullification. The best bet any defendant has in a US court is for the police to make a procedural error, though even then you better be ready to pay a good lawyer to spot it. There is almost no chance of Snowden getting off on a procedural error, though -- for someone that high profile, a lot of care will be taken to ensure that everything is done by the book.
The government also has a lot of power to keep arresting a person and keep putting them back in a court room. If Snowden were not convicted for espionage, he would be arrested for hacking and tried separately for that. If that failed, it would be for tax evasion, illegal orchids, or some other obscure crime. If that failed, he would just be followed by the police day in and day out until he ate ice cream on a Tuesday afternoon in some county in Georgia. Even if the cases are all thrown out, he could be waiting for years to go to trial, and the judge may not be willing to grant someone with his international connections bail.
"Running across the ocean is possibly the most cowardly thing"
There is nothing cowardly about retreating from and avoiding an adversary that has vastly more resources and capabilities than you. Snowden's adversary is the world's most powerful government. It would be stupid not to run.
In other words, what you are advocating is stupidity, and what you call cowardice is what most people would call intelligence.
I'm not making a judgment either way (although I probably have in my earlier comment history), it's just easier for some people to say "Whatever, he's a traitor and a coward" rather than actually think about why he did what he did, what his motivation(s) were/are, and if they ultimately think the ends justify the means.
Indiscriminate dumping of classified data that you didn't look at, to opponents of your government, is pretty much on page 1 of "Compendium of Spies".
What the public got out of his leak was that a) war sucks and b) diplomats are not pure as the driven snow. Both of which the public knew, and have known, and will pretty much always know.
What AQ, TTP, Taliban and other extremist groups got is detailed ground-level descriptions of how the Army operated against them, what informants they used, and much much more. As an intelligence analyst himself, Manning would be in an exception position to understand just how useful those documents would be in their hands, and if we are charitable somehow still judged that the gain to the enemy was somehow still less than the gain to the public.
And this is why Snowden was so careful to note in his initial interviews that he took specific things from the NSA instead of just copying what he could.
However, the most relevant point is that, based on what is being written in the media, there is no real distinction in the average American's mind between the two except that one was caught and the other is on the run. They are both labeled as "leakers" and "traitors" by the government, and except for a few outlets, the mainstream media largely parrots the official talking points. Being treated as a traitor based on a label the government applies to you rather than on the details of what you did is what is really frightening.
The media has little choice about the distinction the people draw though. He fled to Hong Kong, away from a nation where at least 1/3rd of the population still has a jingoistic antagonism to China. He allied with WikiLeaks, who the American people know are at least somewhat more anti-American than anti-secrecy. He tried to get asylum from Ecuador (who is already allied with WikiLeaks), and Venezuela has been chomping at the bit to grant him asylum (I'll let you guess what Americans think about either country at this point).
To put the cherry right on top he delivered his TS-containing brain and his TS-containing gear to effing Russia.
His father has been the smartest Snowden in this whole sorry affair; there's a reason he's worried about the perceived association to WikiLeaks, and that's because it's not favorable to Snowden in the USA.
Running across the ocean is possibly the most cowardly thing, and only further cements his future legacy as a "traitor". Unfortunately one narcissist cannot decide the policy of a nation, and Mr. Snowden has made a mistake in attempting to do so via leaks of classified and top secret information. It's... Traitorous.