I guess what I was trying to say was that Grievous escaping has less to do with any kind of skill he has at it and more to do with the Plot enabling him to do so for the sake of Story Canon. But anyway, the likelihood of him actually escaping from a space battle with Malgus is virtually nil because of the cloaked fleet. Grievous has no way of fending off attacks from invisible persuers, or even knowing if one is sitting right outside his docking bay, ready to blow him to cosmic dust.
No, your right, he doesn't have 'trillions of battle droids'. He's got, and this is a direct quote from Wookiepedia backed up by a source:
I honestly wouldn't take anything from a Wiki related site to heart. It says one thing, but we don't see anywhere near that number in any of the media; Movies, Books, TV and games. Not even if you combined all the droids you say in all those formats together, you still wouldn't see anything close to the number that Wookiee states. Especially when, as I said before, that the Republic senate is worried about a few million more being made as opposed to the supposed quintillions that're on the field. It doesn't make any sense.
Being the Republic, so Grievous has Malgus heavily outnumbered in terms of ships. But I think we can all agree that Sith battlecruisers are far superior to that of the CIS, so they probably count for 3 of Grievous' ships. Still though he is outnumbered. As JekRendar said, Grievous would win the war of attrition. Malgus' only hope of victory is to destroy Grievous' production facilities, or strike at Grievous himself - but Grievous is incredibly evasive.
That I can agree on. In terms of numbers, Grievous does have the advantage. He probably has 6-1 odds on Malgus. Yet as we know, for all the Numbers that Grievous had, Jedi and the Clones have been more than matching them to the point of a near stalemate. The difference here, I'd say, is that Malgus' forces are more varied, with different species and ways of fighting, along with Sith War Droids. Plus Malgus has the Schism Collective, a group of alien scientists dedicated to advancing the weapons and technology under Malgus' command. One such being the Flux Cannon on Malgus' space station, which can completely destroy a Capital Ship in one shot.