I was inclining not to post anything to the "swimming bowl" question. First, it truly seems like a non sirius question, bordering on a prank. Second the answer is so obvious that does not merit a posting to begin with. ASK YOUR CONSULTANT TO CLARIFY WHAT IS A "swimming bowl design and fixed bowl design"
However if you are talking about Ball Valves. There are basically 3 types.
1. - Floating.
2. - Trunion Mounted.
3. - Rising Stem.
Without going into details regarding what are the benefits or drawbacks of each design. I will like to point out that this statement is deceiving: "A floating ball uses line pressure to seal - higher pressure, more force to seal" While in principle it is true in practice it is false.
It is a fact that the higher the pressure the greater the potential damage to the seats. Therefore the greater damage to the seat the higher leek rate. In turn the higher pressure on damage seats the greater the leek rate. Further more, as a general rule the higher the pressure the lower the performance of non metallic materials.
As far as reliability goes, it is subject to the particular application, considering they are all of sound design. But more importantly is to recognize that there are only 2 kinds of valves good and bad ones. When I say "good Valve" I mean good design, good materials, good manufacturing, and good   quality systems. And then in the eyes of the end user it is only "good valve" if it was configured with the right materials and configuration that allows it to perform as a "good valve"
I can’t begin to mention instances that I have been in the field where a Good valve was label by the end user as a bad valve, and in fact it was a perfectly good valve installed in the wrong application. Very few end users of valves will admit this. Even fewer engineers at E&C's will admit they made a mistake when it comes to specifying valves. After all, on/off valves to most people are not important until they need to use it, they seem to think they are just a spool of pipe. They forget why the valve is there to begin with.

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