The good news is that either option looks to be lucrative. It may be worth it to think more about lifestyle and personal preference than hard numbers, however here are some additional considerations to think about:
If you keep the townhouse as a rental, would you be self-managing or hiring a property manager?
You list $714/month principal and interest. What is the breakdown? The $714 is important for cash flow calculations, but the equity you are gaining should also be calculated.
If you sell, consider/research additional expenses above and beyond the 6% realtor commission. I recently sold a house and had to shell out a lot of cash for appraisal, as-built, septic test, and heating system upgrades. Granted, a townhouse might be more forgiving in this regard, but it's something to think about in your analysis.
How long have you lived in the townhouse? If you lived there at least 2 of the last 5 years then the gains on the sale are tax free. Note that this would still be the case if you rent the property for 3 years.