Size and weight do matter but so does performance. If you want the lightest and smaller screen and are ok with middling performance the Surface 3 will work. If you want better performance go with the SP4 even the core m will perform well. (it should be better than the SP3 i3 and near i5 performance although we wont know for sure until somebody tests one). You can get an idea from comparing devices with a Core-M 5y10 to SP3 i3/i5. like the Asus zenbook, Dell venue 11 pro, or Lenovo yoga 3 pro which all have Broadwell Core-M CPUs. The Skylake core m should be a little better than those.