The case for strong SOS vs. weak SOS would be its impact on your post-season seeding and/or team prestige. SOS plays a role in the projection report, which determines your postseason seeding for the NT and PIT (or your lack of reaching either). On the other hand, maybe you just started playing the game or took over a team with a horrific prestige rating. Part of team prestige at the end of the season is determined off your record. In such cases, when you already know the postseason is a dream for down the road rather than this year, it's not bad to schedule a soft non-conference in an effort to horde as many wins as you can...it can be the difference between a C- or a C sometimes, and even if it doesn't make the overall letter grade change, it can make you a "better" C-. There are also minimum win totals needed for the PT (12) and NT (.500 record, 14 generally gets you there). If you're in a real nut-buster of a conference then you want your SOS to at least be manageable enough so that you hit those win totals, and you can afford to do so because your league strength will raise your SOS through conference play. You don't want to be the guy who finishes the year with the No. 1 SOS and a good projection report seeding, but not enough wins because you opted to walk murderer's row.
Sorry of that was tangental, but since your OP spoke of the case for strong vs. weak SOS I thought I'd throw it out there. As far as player development goes, darnoc is spot on with what wrote above.