want to maximize their exposure. Not sure if having two ads in Eros makes a difference, but, I like the different pictures. I assume they do it so they can have more slots in the categories. That is, their ads will appear often in each category, which attracts guys that didn't have a chance to see their other ad.

BackPage providers spam their ads in the DC area because it is measured on how current the ad is. The more current, then the readily available the provider is for that particular time. Also, if they have ads listed in an earlier time, it will be pushed down by newer ads.

Its simple marketing... be seen. Look to one's reviews to see if they are a ripoff. Tineye, backchannels, & other boards can help as well. Also eros has specials like buy 1 ad get another half off this week only which may explain multiple ads.
At the end of the day you go with the reviews, right? So go with the reviews. Cheers, TC