That is a great question. There are several factors affecting access, light rail, and real estate.
The obvious answer is downtown. It is designed with everything within walking distance. You better love loft and condo type living because that is all there is. Downtown has the densest population so naturally it has the most amenities. The also big difference is that Union Station is the hub which makes it by far the most convenient for connections.
The Lone Tree station also built very well around the principles of Transit Oriented Development (TOD). A TOD community is highly walkable and designed where people can live, work, and shop in the same area.
The biggest factor to consider is how walkable is the station from where you live. The Englewood station is the best example of a TOD development on the Southwest line. There are new apartments on the west side of Santa Fe. It is where the old drive in used to be, my wife and I have been there for at least 10 dates, bye-bye drive in. It appears to be less than a quarter mile away from the station. However, there is not a good walkway. You can't have people running across Santa Fe, a six lane highway. The developer and government couldn't agree on terms and prices so that is why that situation appears to exist.
The biggest deal is how walkable is the station, not the train line, from your location. There is also the factor of how to get there. I have done a study on the Denver light rail system. It compared appreciation of properties next to light rail station by distance vs. non light rail properties. I can provide the results if interested. The data is amazing.
I have a proprietary program that takes the mls listings that come out each morning. I have an excel spreadsheet that looks up every property and it can be sorted to determine how far the property is from the light rail station as well as which particular station.
Light rail properties appreciate in value faster than non light rail properties and are cheaper and more convenient for living with access to transit. If you want to work with a Realtor who specializes in light rail properties please give me a call.