As you asked....here we go.....
ARABY
You can field a lot of Cavalry like Knights, Desert Riders and Camel Riders.
You have standard foot troops like Speerman and Bowmen
You have flying Carpets which can add massive firepower at certaion points of the battlefield but which are also a weak unit when being attacked.
You have Elephants which can dish out alot of attacks but which can also "stampede" and kill your own units if you are not taking care of that... I rarely use them in games till 2000 pts as the cost benefit ration is better with oter units till this point value.
Finally .....Araby has a uniqe Magic system.....which makes it sometimes really difficult to decide which spell to use as all of them can give you an advantage.
The trick is the right combination of all of them and to use their unit specific abilities to your advantage.
But for me the most convincing argument is that the models for Araby army are the most beautiful ones for the Warmaster range.
LIZZARDMEN
Simply said an Elite Army. Heavy hitting units that ignore command penalties for dense terrain. In the hands of a skilled player very hard to beat. They have a uique command system as "cold bloode" units onl can get a command within 20cm range but to compensate this the "divind guidance" rule gives them also some real advantage when commanding.
I own them both and played them a lot....despites of other armies.

Frankly said ...in Warmaster each army can beat each army.....if you are skilled enough to use the army specifities to your advantage + having the right portion of luck (as usual when playing a game wher dice are needed)
Regards
Claus