Depends on what your needs are. Are you wanting to purchase it just because it's on the new and latest list?
What do you use your device for? Email? Text? Keep in mind PDA's Smart phones, Blackberry and Droid's all require a data package. Affordability? The Moto Droid is SUPERFAST! ERIS is fast but not as fast as the Moto Droid which also has a qwerty keypad
I choose the HTC Eris cause I didn't need a physical keyboard and don't need the GPS. I may get the Moto Droid for my fiance cause she likes physical keyboards and would use the GPS. So it's all in what you need or are looking for. Both are good phones.
My wife has the Droid and I have the Eris, so I've spent time with both phones.
The Droid is an Iphone killer. Primarily because of the giant display.
The Eris is an Iphone alternative. The first one from Verizon. It's as close to the Iphone as Verizon has gotten.
I chose the Eris because of its size and weight and because of its more polished interface.