Y'know, looking at things, I don't know why people keep saying the SEC has to react to the Big 10's moves (other than to absorb and take over the NCAA).

Let's look at Big 10 expansion:

Penn State, the move that started it all. A+, no denying that. Top-tier program that competes head-to-head with Ohio State and Michigan (their power teams), added a cohesive layer to the East of the geograpic footprint.

Maryland; D- at best. A traditional lesser-bowl team that can't get to any bowls, geographic island over on the East Coast, no relevant competition or improvement to the conference. Big disappointment in basketball, which should have been the effective addition.

Rutgers; F. A shitty program in New Jersey. Nobody cares about them THERE, much less in traditional Big 10 country. They're basically a mid-tier program's homecoming fodder.

Nebraska: A for effort, it was a big-name pickup. Too bad it's like landing a free agent finishing out his career in pro sports... you get the name but none of the accomplishments. I'd say a C- or D with them.

Now, we see USC and UCLA. 1500 miles away, zero rivalries to build outside of the Rose Bowl history, transportation will make every sport outside football and basketball a loss, at least a decade since either has been relevant, adding a big geographic outlier in an area where fans are disinterested to begin with.

Compare that to the SEC-
Arkansas and South Carolina. Both added cohesive layers to the geography.
Arkansas was an A, added a legit challenge to Kentucky in basketball, and banged heads with LSU and Auburn for SEC West titles for a decade.

South Carolina is a B to C. Mild competition in the East until it cratered, then Spurrier brought it to new levels briefly. Built a baseball program, now has a women's basketball program.

A&M and Missouri: decent. Say a B overall. A&M gives Arkansas a traditional rival back, added a cohesive Western layer to the SEC. Mizzou is a bit more geographically challenged, hasn't meshed well with the Arkansas rivalry the league sought, did briefly add some flavor to East football (2 East titles) when it was down, otherwise disappointing. A for A&M, C for Mizzou.

Texas and Oklahoma (incoming):
jury's out, but looks to be a good addition. Texas integrates well with the A&M/Arkansas side, restoring some classic rivalries. OU fits in with that, and possibly helps Mizzou fit in better overall too. You keep the UT-OU rivalry intact, and OU in particular adds some beef to the football side.

TL,DR version- the SEC expansions fit a plan, the Big 10 ones don't.