Well, the Arabs did it too is actualy somewhat correct. If we regard slavery as a way to deal with a perceived scarcity of available or profitable labour then we even have comparable motives although there were a number of differences between new and old world slavery. But let us start at the beginning.

Slavery has a long tradition in northern Africa and what later became the arab world and despite some encouragement to free slaves by the prophet the rise of Islam did not change this. Quite on the contrary, religiously motivated warfare against unbelievers, african "heathens" for example, was an accepted way for the aquisition of unfree labour. Sometimes even muslim africans could be victims of slavery under the excuse that they were lax/ not true muslims.

Regarding numbers, the estimates vary even if we only consider slaves which were exported from subsahara africa to the mediterranean world. But will we count slaves sent to muslim east africa, where in the 19. century plantation agriculture (clove) begun to flourish? Regardless if you need numbers then between 10m and 18m for the time between the 7th century and the mid 20th century are usualy accepted. Depending on slave mortality during the trek north (or east) the number can increase quite substantialy. The atlantic passage might have been hell but i find it hard to believe that crossing the Sahara is much easier. The casualties from resulting endemic warfare are also not included nor does this number include well over a million european slaves caught in the mediterranean and the slaves sourced from the "traditional" balkan areas.

If a slave in the arab world (and we have to use this term very losely and only for convenience) had any advantage over those who suffered in the new world, then it was a certain potential social mobility if they possessed useful skills and were plain lucky (slaves could rise both in the military and at court to quite influential positions). While they also had certain traditional rights (for example appealing to a Qadi when they were abused to heavily and legaly recognized marriage) i would caution against overvaluing them since the difference in power and influence between a slave and a master was still extreme.

If there is one area were the practice of arab slavery can be completely and without hypocrisy condemded then it is the reluctance of the arab nations/powers when it came to ending it, a problem which can partialy still be perceived today.

I admit that this answer is a bit short and certainly not as exhausting as the topic deserves but i leave the in depth comparission to someone else and rather get some icecream :D

sources:

Murray Gordon, Slavery in the Arab World Paul E. Lovejoy, Transformations in Slavery: A History of Slavery in Africa Allan G. B. Fisher, Slavery and Muslim Society in Africa Robert C. Davis, Christian Slaves, Muslim Masters: White Slavery in the Mediterranean, the Barbary Coast, and Italy, 1500-1800