To me, the most important thing in a drum synth is the control I have, the number of parameters that are available/tweak able to shape each sound (kick, snare, etc..). Having a built in sequencer is secondary to me, as well as built in effects. As long as the plugin is multi out I have my needs covered using separate effects...
I am sucker for drums, whether synthesized or sampled. I own a lot of drum synths and samplers (Eg: Attack, Drumaxx, Drumazon, Geist...)
To me, the drum synth to beat is Rob Papen Punch. I LOVE Punch. It offers drum synthesis as well as sample loading and tweakability.
Punch seems to offer more tweakability. Some of the modules have a lot of parameters to shape the sound. Heartbeat seems limited in that respect (just going off the screenshots, videos and info provided on their website). Heartbeat has 5 effects, Punch has 20+.
In the case of Punch, I care about the built in effects because they are modulatable! Very handy for additional sound sculpting/shaping needs that become an integral part of the sound. You can set effects parameters as destinations and modulate them. And they are high quality as well.
I want to try Heartbeat because in the end, it's all about the sound and it might blow Punch out of the water but I have a feeling it's going to be a hard sell. Comparing feature to feature, Punch wins. Sonically, the synthesized Punch "sound" sounds really good. Not to mention that in Punch you can load your own samples (even layer them) and tweak to your hearts content.
The prices are comparable (punch $179 when not on sale, so about $40 cheaper than Heartbeat), and Punch also comes with Punch BD, a separate drum synth dedicated to shaping and layering kick drums.
Punch also comes with a gazillion high quality presets. Not sure how many Heartbeat comes with.
Oh, and I like the GUI of Heartbeat. I am digging the Frankenstein method to represent each section, as described in one of the posts above
