I started orks because of the "I don't care" attitude the orks have about caualties. They are not a dying race, and there is no "sadness" after a battle for the dead, just a celebration that they won and can fight another day. Then the fact that they will fight against and with anything and any race, to one day be allied with chaos marines, and the next day be allied with the tau against them, then turn around and eat the tau...
The other races have story lines where they are losing their world, empire, survival, etc. except nids, and orks are the only race to eat nids. Orks enjoy war, do not seek peace, could care less if other orks die, (means more for them) and if they get kicked off a planet then they will just come back in a few years with more orks.
As far a modeling goes, anything is good enough, there is no need for parade ground perfection, as mentioned before orks don't care. This means that no two of anything looks alike, you can have a BW made from a land raider, and another made from a Leman Russ, and another actually using the BW kit and they are all perfectly acceptable.
Also there is no wrong way to paint an ork, yes there are a few recognizable patterns by clan, but if you have a truck load of moons and a big mob on foot of evil suns it is ok, only another ork general will notice and of course won't care as long as there are orks on the table. Of course there are the silly painters who give their orks clown outfits, but that is ok, as long as there are orks on the table. if you painted CSM as clowns you would receive much derision and smack talk, with orks, well... they are just orks.
Then there is army composition, of course there are a few elitists (such as my self who plays speed freaks) who like their army a certain style, then there are others who change their list and style almost weekly. Of course there is everything in between.
lastly orks are fun and funny, if a grot shoots and kills a SM character with its lousy shooter that is funny. When a group of boys drive up in a truck and shoot a bunch of terminators who fail all their saves, that is funny, when a single nob kills a carnifex, that is funny, when the war boss drives up to your opponents prize unit and kills it, that is funny. Of course when 30 shoota boys fire and cause no wounds that is funny, when 15 tank bustas can't even kill a rhino that is funny. The whole army is just unpredictable and no unit can ever be cheesed out to be relied on as the game winner. One game they will rule the board, the next game get sent packing by a single guardsman with a pointy stick. There are a few units that can be tricked out, and can have a good chance to perform well, there is no guarantee, unlike certain SM units (like cheesinators) that are heavily relied on and if it gets killed they think the game is lost. If an ork unit is killed... oh well, we have more of those.
So, there is no short answer, just a whole lot of fun with a whole lot of models that you can't paint wrong.