Droid 2 comes with a physical keyboard, and is quite solidly built with metal. The slider feels precise and smooth. It also has better battery life than the Droid Incredible and offering more battery management options. The graphics performance of the chip of the Droid 2 outpaces that of the Droid Incredible.
The pluses for the Droid Incredible is that it has a more elegant interface with HTC Sense. The software keyboard of the HTC is quite impressive and I find never a good reason to replace them with a third party software keyboard. Great set of widgets too. HTC in my opinion, seems to tweak Android the best. However, the phone has miserable battery life, and you definitely need to get a spare battery, hopefully the 1500mah battery from a Touch Pro 2. The colors are more vibrant on the Droid Incredible and blacks are blacks thanks to OLED but the screen on the Droid 2 is sharper.
My personal experience with the Droid Incredible is one that justifies its name. Incredible. But you cannot overlook the advantages the Droid 2 has with its screen sharpness, the solid metal build, the better battery life, physical keyboard and sharpness. Oh and plus the fact it comes with more built in memory out of the box. Verizon rated it as historically, the lowest return rate of any smartphone they ever sold. JD Powers got Motorola squeaking out HTC in consumer satisfaction in smartphone.
There is a new HTC smartphone that is soon coming to Verizon, that has a slider but has Bing Maps and Search over on Android which is sure to annoy people, although you can install Google Search and Maps from the Android Market. Currently code named the Merge, its comparable to a Droid Incredible with a slider keyboard, and can roam on GSM with a SIM. While the CPU clock is lower than the Droid Incredible, its a new generational one so it matches the old one in speed, although I would still rate the Droid 2 ahead in graphics speed.
Still overall, I don't find any significant advantages the Merge has over the Droid 2, which I consider the best Android on Verizon right now short of the Droid X. I would personally still pick the Droid 2 over the Merge. One other point is that the Merge appears to be the Verizon equivalent of the G2 phone with T-Mobile, which has some slider mechanism issues. Bearing this in mind, I would feel more confident of the slider and the Droid 2's overall build.