I would have to disagree slightly with the Soldiers comparison since these games play totally different from one another. I picked them both up and loved Soldiers and although I am only a few missions into Panzers I am enjoying it as well. One thing to note I dont usually play RTS at all but I do like games that deviate from the norm of the genre.
Here are the differences as I think of them.
Soldiers: Slow methodical gameplay.
Panzers: Action RTS, battles are bigger and louder usually with tanks, mortar, infantry, artillery, etc.
Soldiers: Careful planning is nescesary to work your way through the objectives.
Panzers: You can be a bit more gungho here but thinking is still nesecary.
Soldiers: 1 small squad at the start of each mission most of the time within missions you are using soldiers and few vehicles.
Panzers: Use prestige points after each mission to buy units for the next mission, unit are also given to you. Tanks and artillery play a large part in the battles. You control squads of infantry instead of individual infantry units.
Soldiers: Total realism and a realistic damage model for units, knock tracks off tanks, damage tank turrets, buildings crumble when shot, gun emplacements are instant death.
Panzers: Realism reduced, units have a health bar(including buildings) any infantry within the unit or building ejects when unit is destroyed.
Soldiers: Direct control of units, every RTS should have this feature. Slow motion mode.
Panzers: During missions you can call in bombers, bombing planes, paratroopers, recon planes, and artillery as they are available.
Graphically they are both really nice although Panzers does run faster for me even during large scale battles. They both have coop mode.
There are two demos out for Panzers and one for Soldiers.