First off, its about time.
Great work as usual, Artcore. Have you adopted the same basing method for all your Marines? I thought it was just the Sternguard but Joe Marine makes me think again.
Also, powersword looks good. What helped me out was this
http://www.heresy-online.net/forums/showthread.php?t=6438 from Heresy Online, but you need to modify it to suit your colours and stuff. Just thought I'd throw it out there.
Digging the combi-melta dude. He looks really heroic and Ultramariney with his swept back hair and iconography.
Good use of the head on that Sergeant, ties it back into the rest of your army nicely. You want them looking elite, but not too different. The Greek/Roman style helmet brings it together.
I like the red on the bolter. Really think you should drill your barrels, though
. Maybe, if you're stuck for bolter inspiration beyond the targetters and drum magazines, you could finely do some irregular lines in white paint on the large empty parts of the casing for writing - scriptures and litanies and other Marine stuff. Just a thought, which might not even look right. I'm just thinking about the model that's painted. He lost the DA iconography and its now looking a bit flat. Not bad, really, but its a thought.
On the banner, if you can separate the U symbol from its backing, it'd look better than set into that square of plastic, I reckon. Mounting them will be tricky. I'd take a very small pin vice to it - check the width of the drill bit against the metal you're gonna insert - and decapitate the skull. Drill straight down into the pole, and then up into the icon you select (not very deep, mind). I manage to pin my DA swords (from the Ravenwing and Veteran sprue - the big swords) into the hands of Tactical Marines using this method. You just have to be careful with it.
And having typed all that, I realized you're only asking for an opinion of which to use
. If you can hollow out the Ultramarine symbol from that blocky background its set in (personal preference), then I'd go with that. Otherwise I'd go with the eagle. I think the blocky square thing detracts from the symbol otherwise.