seeking advice of phone to buy

A

AC Question

I'd like to buy something with a lower budget.
Currently using an old phone Huawei ascend P1 which has icecream sandwich OS…it is now too laggy. I am not a heavy user and do not play games. Objective is to have one that can last a few years but I am not as picky as most of you so I guess a phone capable of running marshmallow 3 years later without much lag can satisfy me. I am now wondering the difference of nexus 5 and LG G3 with 3G RAM/64G. As time passes which one of the two will meet my need with a larger chance? The nexus 5 is already on marshmallow and can be upgraded to nougat unofficially. But it has only 2G RAM I don't know if this would be a driving factor that will make it incompetent compared to LG G3 (3G RAM), especially when in the future all apps become heavier. The G3 with 3G RAM sounds good but as I read the reviews its 1440 screen and bloatware eats the ram and its superiority is not that large as compared to nexus 5. Is my understanding right? I am now looking at the two refurbished ones under $200. Which would you recommend?
And how do those two compare to galaxy S4/5?
Comment purely based on my needs (i.e. performance smoothly in future). You can ignore all other features such as camera, display etc.
And I also saw the oneplus 2 with 4G RAM with a few dozens of bucks more. but a lot of negative reviews. Is it better? I also appreciate any other recommendations!
thanks in advance