No real additional benefits to holding SE from what you get flying upfront revenue and being an Elite (assume for US lounge access). Keep your miles going to CO/UA and earn 1K since you won't be hit with all those surcharges when cashing them in as would be the case when using AE miles. You'll also get 100% bonus putting AC flights into CO/UA while being Elite you'd only get half that many. Also, booking one way STAR awards is not always possible with AE, however is easy to do in the CO/UA program (using the CO booking engine) and these only cost half the return "price" while in AE it's about 66% of the return "price". I'm top tier in both programs mainly because I don't fly revenue Exec on AC (just upgraded T+) so find SE benefits of use. Keep doing what you're doing unless you find the merged CO/UA program next year isn't delivering.