If you plan to fly SK for most of your TATL flights, it's best to accrue your miles there so you have miles available for potential upgrades. Also, if there are op-ups when M is oversold, you have a better chance of being upgraded as a solo flyer with Silver status than no status.

I'm not sure how often it happens any more, with the OT upgrades, etc., but many times in the past when I approached the counter to request a standby upgrade with points, my husband and I were upgraded free as EB Silver members because the flight was oversold and they were going to upgrade someone anyway. It always surprised me that they didn't take our points anyway, since we'd offered them. However, this is going back a few years so YMMV.

If not EuroBonus, what other programs were you looking at? You will want to credit the miles from all your Star Alliance flights somewhere. You could look at doing so on UA/CO or LH but you wouldn't likely gain anything by that unless you think you could reach Gold on one of their programs, giving you access to the lounges.

Another advantage to crediting with SK is that they have the monthly bonus offers where you can get award trips often for half the normal required points. So if you wanted to take a long weekend somewhere within Europe, you might find you've accrued enough points to do that. There are also hotel partners. In the last two years, my husband and I have taken two long weekends to London (in Y+/C) and had a 3-night stay at a hotel in Sweden using our SK points since we hadn't had a chance to use them up on SK TATL flights.

Susan