HSPA/HSDPA/EDGE/GPRS means you can be pretty certain to always have a connection wherever you are, almost anywhere in the world these days. But as said, roaming is usually very expensive.
WiFi is amazingly cheap or even free, but not available everywhere.
In other words, have both, and use WiFi whenever it is available. For non-roaming, HSPA is outstanding, so one probably wants that for use 'at home' anyway!
HSPA/HSDPA means you won't be needing ADSL or a cable modem at home either, depending on pricing for non-roaming access... But that's another story...
