Having never compared identical brews done with both fermentation procedures, I can't really say for sure.
I use a 6.5 gallon carboy for my primary fermentation and get blow-off through my blow-off tube only about 25% of the time. Every beer I have brewed has met or exceeded my expectation. I haven't noticed offensive bitterness from those that did not expell through the blow-off tube.
I'm sure that it can't hurt to get rid of that foam but I don't worry about it when it doesn't. That stuff will settle to the bottom when the krausen falls anyway and will be left behind during the transfer to the secondary.
Either way, it get's left out of the finished beer.
Secondary #2: Empty
Bottle Conditioning: Oatmeal Stout
Drinking from Keg: Ordinary Bitter, Kolsch
Drinking bottled: Brown Autumn Wee Heavy
Peaches and Cream Weizen
"This is grain, which any fool can eat, but for which the Lord intended a more divine means of consumption... Beer!"
-Robin Hood, Prince of Thieves, Friar Tuck.
Next up: Hefe Weizen