Another thing to consider is the fermenter geometry of both the better bottle and the Mr.Beer. I used the Mr. Beer for a number of batches and it worked just fine. I would say that if you fermented two identical recipes side by side in the two fermenters, you would get a slightly fruitier beer from the Mr. Beer for two reasons. One, it is a short, shallow, and long shape.
Second, it is getting close to an open fermentation with the way the lid is notched. Depending on the types of beers you are doing, this could work to your advantage.
You can control the fruitiness and esters with the better bottle by the type of airlock you use. You want more esters, simply use a piece of sanitized aluminum foil over the top during primary like a starter. I've done this with a number of batches and have been very pleased with the results, and so were the judges.
Personally, I'd go with the unported better bottle and use a racking cane and syphon to get your beer out. Then just clean it by filling her up with PBW and socking her for a few hours. With Mr. Beer, it's easy to be tempted to scrub the insides and scratch it up.
If you want to sample the beer at any time, just get a wine thief. You'll keep on using that thing until it falls apart. It was one of the best and cheapest investments I have made.
Cheers!
Live and Learn. Then get drunk and forget it all.
On Tap: Naughty Monk 12 - BDS, Redemption Brown, Silver City's Big Daddy's ESB