I *LOVE* this game, even if people find it repetitive in tournaments/leagues.
First off, I'm not claiming this is THE strat, it's just mine when I am in competition:
1- Choose 7 (I can never tell if you keep 7's attributes post lock swap, but it seems to, so I just do this), lock ball
2- Choose 1, earn Escape letters by shooting into bumpers. STOP when video mode is ready
3- Lock Second Ball. NOW. Decision time. No matter what happens at this point, I'm going to attempt to hit loops. Not just for Sonic Boom, but for the multipliers. Sonic Boom strategy is definitely a great strategy, but if I don't set up MB and video mode, I'm leaving major points on the table for when I eventually flub the loop/W-H-O. SO. Am I confident that I can rock out the upper loop on this specific Dr. Who? If yes, then I choose 7 again (1 is done after video mode is set). If not, I choose 6 for the extra help earning multipliers.
4- I have my loops done and I am at max multipliers and the ball is on the lower flippers (and Sonic Boom is obviously not running). It comes down to starting video mode or hammering the wall for MB. It all comes down to how much progress was made on the wall and making a decision quickly, before my multipliers go down.
5A- If I do video mode, I *commit* to video mode until I've defeated the final wave (and earn all 7 Doctors + the 7 Doctors bonus, which I've received 60million alone for in some cases ON TOP of the video mode completion score). Video mode is a lot of lower scoring chunks of points spread out, but they accumulate. There is also the rules bonus of earning all 7 Doctors, which opens every strategy up to me from that point forward.
5B- If I choose MB instead, well, play out MB. Getting all the way through MB and defeating Davros + max multipliers can be a 1.2 billion reward all on its own (not counting any other Daleks you defeated getting there). That's a ton of loop shots that my opponent needs to make in order to catch up.
6- After completing either video mode or MB, it's back to setting whatever I just completed back up. Get balls locked or re-set Video Mode. Then repeat from step 3...as in...hit loops to up multiplier/milk Sonic Boom, then make a decision on either Video Mode or MB.
It's the strategy with a lot more risk involved than straight Sonic Boom, but it gives me insurance that I can knock out the other high scoring opportunities for when that upper loop war of attrition is finally lost, yet my multipliers are maxed.
Just my 2 cents. I love this game.