Sirius vs XM Reception

I am a long time Sirius subscriber (pre-merger) and have had seamless rock solid reception on my commute down I89 in New Hampshire for many years. Last year I purchased a new Toyota Corolla with built in "Sirius/XM" radio. Reception was terrible. I looked into the problem and found that Sirius and XM have different satellites and Toyota installs XM in their vehicles. I moved my portable Sirius Starmate into my new Corolla and was back to rock solid reception again. The problem is that XM satellites are in fixed position over the equator which requires a lower angle of reception which is closer to the horizon and more susceptible to blockage by mountains, hills and trees (which we have in New Hampshire) The Sirius satellites move over the United States, which means a higher angle and not as susceptible to blockage by mountains etc. As long as Sirius is an option, I will remain a subscriber but XM is unacceptable.