Why do you think MQ is good?
Because of the customization of abilities.
Each item for the mech and each mech is different, so new setups can be tested with each character. DPS, DOT, Energy Drain, Tricks. And nothing binding such as a class, as the variety of mech bases makes the concept of classes just archaic
Why do you think it's bad?
Bad scaling and horrible difficulty curves near beginner levels or even for people who make bad choices//are broke.
The energy sword combat is impossible a lot of the times if you haven't taken the course a bunch of times to get a decent weapon. And the course itself is a horrible grindfest. Strong attacks and Defending don't seem to make much of a difference, and sometimes if you get a weak strong attack, you've essentially wasted a turn (Getting 3 dmg with a strong attack multiple times while you could have done 5 damage with normal? ;__;)
If you make a bad choice or somehow get stuck in the scaling, it may be a giant chore to gather up enough money to purchase a weapon or mech that makes it so you don't die to things your current level.
What makes you play MQ over other games?
The game is more interesting and has more choices, along with the ability to buy everything instead of hoping to find it (Although loot equipment is a good thing to have as well, just the rare shops and everchanging stores provide more variety).
The combat doesn't take as long and usually can be done very quickly as it's always 1vs1.
The free content is always decent and doesn't seem too underpowered by the paid content, and the StarCaptain content isn't overshadowing the entire game. Sure, it provides neat features -better weapons and weapon abilities on some rares, along with difficulty adjustments and some more advanced story stuff- but in the face of the entire mechquest library is a well deserved bonus for those who pay. (Instead of it being almost over half of the entire content)
*Note: yeah, I'm a free player, but I've been more tempted to pay for something on MQ than I was on DF. *
What doesn't make you play MQ over the other games?
Nothing. I drifted away from the other games and spend the time I wouldn't have anything to do on MQ, and usually play MQ in times of wars to see what new items and mechs they have.