Have been using all three networks (Claro/Movistar/Personal) - my, somewhat subjective, observations:
- Claro = best coverage on the ruta and out in the province, but I found myself without signal at times downtown (I am not using it any longer)
- Movistar = best coverage on the Rio (if you are out sailing), sometimes lousy 3G
- Personal = speedy 3G/EDGE in the downtown, not that well out in the country
If you are most of the times just staying in the city, I think your best choice would be the Personal Black no-worries-all-included-plan...