Totally depends on which Lenovo. The consumer grade stuff from Lenovo (IdeaPads) is okay; Thinkpads (business-grade) are great.
I've known plenty of people first hand that bought cheap Acers and they lasted several years without trouble. However I could never recommend an Acer over a Lenovo especially if the prices are similar and the Lenovo has more ram (!!!). Are you buying this laptop to play games?
IMO don't even consider any laptop that has less than 4GB of RAM.
IMO you can consider laptops with less than 4GB of RAM because it's so cheap that you can just buy it after and stick it in for around $20.
They've made upgrading RAM (and even hard drives, surprisingly) very easy on laptops these days. Quick access doors on the bottom. Takes less than 5 minutes.