I personally recommend using Aventuras Patagonicas for your Aconcagua expedition for the following reasons: They have great logistics on the mountain, and logistics is key to success. Being ill prepared on this mountain not only decreases your chances, but as history keeps repeating, it can be fatal. It is not worth using a cheaper company or compromising gear to save $500. Up there you need everything to your advantage. Everything from their meal planning to packing to mule provisioning to the highly skilled American guides they used was excellent. Just a quick look at other companies on the hill was all that was needed to tell we were the best prepared and provisioned team up there. We had the cool Mountain Hardware tents; got morning blood-oxy readings daily; used Grajales for the mules (they are the oldest and most reliable mule company in ARG); and the Guanacos Route, in my personal opinion, is superior for acclimatization.
Your success on Aconcagua depends on many factors, the least of which are certainly not your pre-trip physical prep, mental preparedness and fortitude, the quality of your gear and some serious luck with the weather. Because there are so many complications that can deny you the summit which may be out of your control, it certainly makes sense to max out on the things which can control; because for the price you pay for guided expeditions, it is always a real shame to come down off the mountain with failure, when problems you may have had could have been avoided by better planning. Using A.P. is part of great planning and I am not too proud to admit that my success in February 03 of sumitting was partly because of their great program. Come prepared and take the pre-departure gear check in Mendoza seriously. Augment their food by taking some of your favorite nutritious lunch snacks with you (like beef jerky, tuna and high-protein energy bars); the lunch snacks available in Argentina are marginal, especially for your high days when your appetite will be pretty awful. Most of all enjoy the stark beautiful Andes; summit or not I am sure you will have the adventure of a lifetime.
Brian Ward, Marina del Rey, CA