I think both are good but it depends on your team. Get the one that counters the others' weaknesses
Which pokemon is better, crobat, or houndoom?
Houndoom is better it's got a mega evolution which makes it faster and
Deadly with STAB Flamethrower and solar power to make it a bigger threat. It has higher defenses at 90 than crobat at 80 and more deadly
It also has STAB dark pulse
That lies in what you want if you need speed you need crobat, but for fire power you need houndoom
I, personally, think Crobat is better. It's wicked fast, and although Zubat is one of the most annoying Pokemon to train, it's worth it. Once it becomes Golbat at Lv.22, you'll be glad you trained it. But then again, I've never raised a Houndoom before... It really depends on what you want, which one is better. Do you want an awesome flying type or an awesome fire type? Heck, get both!