ome players expect Warmaster to be a "little" Warhammer and discard it as soon as they realize that it is not. This is a mistake because Warmaster is a very good game on it's own. There are some common issues, but also a lot of differences between the two game systems.
On miniature size
The most obvious is the size of the miniatures. Warhammer miniatures should be painted for the cabinet as well as for the gaming table. Warmaster miniatures are very good and highly detailed for their size and while some of them surely deserve a place in the cabinet of "best models produced ever" they are generally designed for the gaming table. And their visual impact on the gaming table is immense. Any painted Warmaster army will look great on the table and the armies will move and look like armies for the whole game. The rules for brigades and the restricted speed of units not in line or column formation support this. While in Warhammer a regiment always looks like a small band of warriors, a Warmaster brigade (more comparable to a Warhammer regiment in terms of use) looks like a big military unit. This is no surprise if you remember that the average Warhammer infantry regiment of 20 warriors is compared to a average 4 unit infantry brigade of 118 to 144 single Warmaster miniatures.
The size of the miniatures allows the designers to bring warmachines and monsters up to scale. While a Warhammer dragon miniature compared to an Warhammer warrior is not as impressive as it's fame, the Warmaster monsters size holds their ego easily.
On army size
In average you have about 20 (up to 4 of the artillery) units and 3 to 6 characters in a 2000 points Warmaster army. In Warhammer it is more difficult to anticipate the army composition, but about 7units (up to 4 artillery pieces) and 4 characters is probably what you have to expect. While characters and artillery are about equal the difference in units jumps to the eye. But there is not so much difference in game terms. The Warhammer units operate separately, but the Warmaster units in brigades. When you take into account the artillery and brigades you will have between 5 and 7 operational "units" that will move about the battlefield
On profiles
The difference in statistics and the number in different unit types is smaller in Warmaster, but because of the game system the differences are quite noticeable. The difference between a High Elf spearmen (save 5) and an Empire halberdier (save 6) is bigger than the 1 point of save suggests, because of the big number of dices rolled . All Warmaster armies are quite different in terms of playing style and have their own character besides the reduced profile.
But more importantly the Warmaster profile ensures that any Warmaster unit has a good chance to cripple any other Warmaster unit, while in Warhammer the profile differences are sometimes so huge that all you can do to hurt your opponent is to drop his miniatures on the floor.
On gameflow
These are two completely different game systems a comparison is out of scope. The visual representation of a battle and more importantly it's flow is better in Warmaster. You have recognizable battle lines and the armies move quickly about the battlefield. You can make out defensive positions, strong points, attack forces and flanking maneuvers just by looking on the table. There is no need to reference the player's army list to see whether something is hidden in a unit that changes it's use completely. The ranges and effect of shooting are limited, so a purely defensive on shooting relying strategy is not possible and usually both players are forced to maneuver and attack to win the game.
A problem beginners encounter often is the sudden end of a Warmaster game. This happens mainly to beginners for different reasons. Often the battles are small so that the loss of 4 units will break your army. A decisive charge killing a brigade will end the game. In bigger battles the loss of a brigade will obviously be not as crucial. More experienced players will try to avoid such a decisive charge by different means or will stretch his army in a way, so that the loss of 4 units in a turn is unlikely. There are other ways, but this is not the topic of that paragraph.
Warmaster seems to be more dependent on movement than Warhammer, because the miniatures can move so far in a single turn and transferring a unit from one flank to the other is quite possible. But movement is as important in Warhammer, because the one who decides which units fight where is the one who most likely wins.
On characters
The importance of characters in both game systems is immense, but for different reasons. In Warmaster the characters give orders and missing or failing a order can be crucial. Warmaster characters usually don't fight and even when they do it, it usually does not matter except when the character is mounted on a dragon and preferably has a magic sword of some kind. This is quite expensive. For a character like this you get 4 infantry regiments or 2 medium cavalry regiments. Something that puts the "fighting character" into perspective. Still there are situations when a fighting character makes a difference, but generally the units you can by for his cost are a much better investment. In Warhammer (also in 6th edition besides all comments from the designers) the characters are formidable fighters and often the only way to strike back and/or inflict damage on an enemy. In Warhammer a single character can still hold off or even beat a unit of warriors, something that is impossible in Warmaster
On spells
The Warmaster spells are mostly supporting and not devastating. In Warhammer there are spells which tip the balance quite strongly and kill a unit in a turn. If one Warhammer army has a big magic superiority the game gets frustrating to play (for the oponent). The player will get many spells through and there is more than one spell that does really hurt. In Warmaster there is a big restriction on spells. Most armies can try to cast one spell per turn and 1000 points, some armies can try two spells. With the restricted ranges and relatively high (compared to Warhammer) difficulty to cast a spell magic can make a difference, but doesn't do so most of the time.