"Better of the two"? don't know that there's a hard, solid answer for that one. They're basically the same rifle with different stocks.
I have owned Sendero's in 7Mag and .300Win. Both had blued, solid barrel's and were crazy accurate. They inspired me and alot of on-lookers by making shots at distant "objects" look too easy.
I shot the .300 for a while, convinced myself I didn't need it and traded it for a beautiful 70's vintage Rem 700 Varmint Special in .243Win.
I kept the 7mag until last year and traded it. The barrel was on the way out, so I swapped it for a PSS in 7mag. It would still shoot .5" and better on somedays but would take me all day to get the copper out. The first 12" of the bore had become very rough, from heat cracks I believe. You could feel the difference with cleaning patch and rod.
I really haven't shot the newer rifle alot, yet. I've tried a few loads with the 168 SMK, 154 SST, 150 Scirroco, 150 NBT and it didn't seem to like that weight range. I did get sub .5" out of the 140 TSX, which makes me very happy as this is an awesome bullet. I make give the 140 NBT a try also. So far, the PSS is not filling the shoes of its predecessor.
I traded that sweet little .243 for a .25-06 Sendero SF. It shoots (period)and will probably stay with me for a long while. It will sling 75gn Sierra HP's at 3500+fps, 100gn Nosler BT and Barnes TSX's at 3300fps and 115gn Bergers at 3100fps all into one ragged hole.
In my experience, the Sendero shoot. I can't speak for the Sendero II's. The PSS may come around, if it does it can stay, if not I'll find it a new home. JohnnyK.
"The pleasure you get from life is equal to the attitude you put into it."