Semenyih landed from my perception is not for rental play, if you think rental is essential, then perhaps some condo nearby colleges/university would be your main preference.
EcoMajestic, as applicable to Setia Ecohill, from my opinion would be more oriented on capital appreciation, be it own stay or investment. It's is fairly hard you can find such great township with this scale around KV already, you only can reap the actual benefits after the township move to mature stage, presumably about 5 years from now. Of course, holding power is a crucial factor here.
In terms of distance, don't judge based on current road/traffic/distance using the "suffocated" Jalan Semenyih. As I mentioned many times, as soon as the Ecohill Link is ready, you can totally skip the Jalan Semenyih, and reach the township directly from Lekas.
As I have shown in my previous post, from Semenyih Lekas exit till Batu 9 toll Cheras just merely 20 minutes away, from Semenyih Lekas exit to Setia Ecohill will be just stone throw away.