there has been a few discussions on weldin up the hood seam here on the Bolt, try a search an see if ya find a answer ya like.
There are lottsa opinions on the longevity of a welded up seam and crackin of the filler later on.
Mine came Bondo'ed up and cracked it took me a full day to remove all the crap that was in there from the P.O. and I went with a stainless strip down the center ...I really like the look, but it is YOUR truck do what trips your trigger and enjoy it!
All I will say is at todays highway speeds of 65mph my hood shakes a little and a little shake will eventually lead to a crack in bought ANY filler used.
Just my 2-pennies
Tim