HSDPA: An enhancement for 3G UMTS networks, High Speed Downlink Packet Access promises bone-rattling speeds of up to 14.4Mbps, compared to a "mere" top speed of 2Mbps for UMTS.
EDGE: Enhanced Data rates for GSM Evolution (or Enhanced Data GSM Environment), a 2.5G enhancement for GSM with a theoretical top speed of 200Kbps, although real-world speeds will be closer to 90Kbps.
Their is more of a difference than you might think...and as the networks evolve the potential to reach those top speeds become more of a possibility but certainly at it's slowest expected connection it's much faster. I've toyed around with my old E61 and cingular video using an Edge connection and also seen the LG 3G in action and the speeds are dramatically different. It's even more of a testament to the speed considering the E61 has significantly more Ram and processing speed than the LG