Let's say you are dead set on betting 1 unit on the over in an NBA Game. Your site has:

Over 200 (-110)
Under 200 (+100)


They also have Team Totals:

Team A Over 103.5 (-105)
Team A Under 103.5 (-111)

Team B Over 96.5 (-104)
Team B Under 96.5 (-113)



Without having any opinion on the spread, the obvious play to me is half a unit on Team A over and half a unit on Team B over. The juice looks more favorable, and you are more diversified.

Am I missing anything here?

if 1 team goes over and 1 team goes over but they woulda combined to hit the game over, u lose juice instead of just winning your single bet

Diversification works both ways. You can go 1-1 when the original bet would have lost, or go 1-1 when the original bet would have won.

I see it as two 5% ROI bets instead of one 4% ROI bet. Unless I'm missing something, which I have in the past in situations like these.

The distributions don't necessarily add exactly. In a more extreme version, like a soccer 1h or something, say you have a distribution with A o0.5 and, B o0.5 50% fair identical distributions and no correlation, so both A and B get at least one goal 50% of the time, and more than 1 goal X% of the time (and exactly 1 goal .5-X obv)

So 0-0 happens 25% of the time, 1-0 and 0-1 happen 2*.5*(.5-x), 2-0/0-2+ happen 2*.5*X, and 1-1+ happens .25

So even though both of the TTs are o 0.5 +100 fair, o1 +100 is +EV (assuming X>0 and teams ever score 2+) because it wins .25+x and loses only .25.

The effect is much smaller adding NBA TTs to make a game total, but I think your two options are about the same. Don't play the TTs at -108 vs their sum at -110 though.

That's why he's a first ballot HOFer.