First it depends on what you're question is - i.e. what do u mean by better? Are you talking better for working the shoulder, or better to avoid injury?
If it's the former, then it depends on what portion of the front delt you want to work. While all seating positions on the seated shoulder press wud work the front delt to some extent, diiferent portions will work different portions.
Different ppl will prefer diff angles but I prefer 90degrees with a barbell militry press, but a slight angle with DBs.
As far as which is better, in terms of lumbar support I would reckon 90degrees would be better.