1. value is very subjective and personal. the base aluminum versions are the same watch and they are very sturdy. further most OTHER people will hardly tell the difference when on your wrist. the higher end versions are for YOU.
2. the sapphire screen essentially does not scratch, that to me is the biggest thing with stainless and Ti versions. but remember... the glass version doesn't scratch much, its only visible to you, and only when the screen isn't lit mostly. so is that worth it to you?
3. the most sturdy version of the apple watch is NOT the Ti version. it is the versions of the stainless that have the DLC coating, currently the dark gray version (forgot the name). these essentially don't scratch either. i mean you can, but i beat the hell out of mine for 3 years and you almost need a microscope to see anything wrong with the finish. the DLC dark Ti is pretty sturdy too but slightly less so. regular Ti will scratch and you can't fix it. regular silver stainless scratches like crazy BUT its the only finish most think looks NICE weathered with lots of fine scratches, and you can polish them out if you really want.
bottom line... if you have plenty of extra money and are very bothered by the fine scratches the base glass and aluminum version gets etc. get the DLC stainless versions or DLC Ti versions (stainless is the strongest) but if you don't think your current apple watch is that bad stick with aluminum and maybe treat yourself to upgrading more often with the savings.
