Which is better and what should i get the iphone 6(S) VS iphone SE?

So i want the apple watch requires iphone 6 or later so my options are 1. Iphone 6(S) with 16 GB for $330.00 vs iphone 6(S) with 64 GB for $400.00 or vs the iphone SE for $200.00 with 16 GB so don't know which one to go with and to make matters even worse i have the iphone (4) so no matter which one i buy i have to go through my carrier to get it activated at the store and since i have the iphone (4) i'm currently used to that make / size iphone so if i get the iphone 6(S) there's only a 70 dollar difference for the 64 GB or the 16 GB or 16 GB iphone SE is 200.00 dollars so if do go with the iphone 6 (S) then there's the $70.00 dollar difference between 16 GB and the 6 (S) with 64 GB and if i get the 6 (S) with 64 GB i won't have enough to afford the $80.00 Lifeproof case for it or the $ 65.00 dollar otterbox Defender series to protect it and i would like both otterbox and Life Proof so something happens to my Life Proof i have the otterbox as a back up and if i do spend the $400.00 i'll onyl have $5.00 left over so again which iphone is better the 6(S) with 16 GB vs 6(S) with 64 GB or iphone SE with 16 GB due tot heir prices

That decision basically comes down to what screen size you want. The SE is basically the 6s in a 5s body.