Can't comment on either but every D-Link piece of hardware I've bought has been a dog. Netgear is not too flash either but still ahead of a D-Link.
Choose the Netgear because it has dual band support. You will only get a maximum of 130Mbit/s via wifi if you are stuck using 2.4GHz on 802.11n. The DIR-645 doesn't even have gigabit ethernet ports so good luck getting more than 100Mbps between your wired and wireless net :)
One thing I must mention is an all in one solution like the DGND3700 will never be as good as a standalone product. I personally have a cheapo $30 TPLink ADSL modem that only does 1 thing - but it does the ADSL thing well. I can swap WiFi access point whenever I feel like without having to worry about ADSL issues.