Check smartphone magazine online. Under a year ago I'd say they did a review on all the GPS apps. Start there and then make a decision.
I tried to google for the article and was unsuccessful, I didn't try too hard though.
If you check their annual best software awards (currently only at 2008 since 2009 isn't over yet) you can find best GPS software and they divide it by voice guidance apps and non-voice guidance, etc.
http://www.smartphonemag.com/cms/awa...nners_ppc_apps
I think a lot more voice guided gps apps are available now though.