you can always buy old iphone models like the 3gs, 4 or 4s. in mi3 you feel the lag because miui is a heavily skinned ui compared to the stock android. I use mi3 for 2 weeks but decided to sell it off because I dont like getting stucked with miui (even kitkat take so long, google already about to give L). mi3 could have been a beast with custom roms.