Some points to make:
1) Synthetic media, even at a higher efficiency, flows better than cellulose or blended. That's one reason why it's becoming so prevalent... a "best of both worlds" scenario.
2) Do you mean base end bypass? If so:
a) IN THEORY, it's better but in practice, it doesn't matter much. This according to many in the filter industry. We like to debate what's "best" and that's fine but the scenarios in which "best" matters is only a tiny fraction of the real world. The location of the bypass is only important when or if the oil filyer bypasses. I started wondering how often that happened and when I interviewed a number of oil filter folks for
THIS and other outlets, I discovered that bypass is "infrequent" (a quote from one engineer) for most people. There are situations that make it more common. The experts wouldn't pin down anything better than "infrequent" because it can vary from application to application so I installed a differential pressure monitoring setup onto my own truck to see for myself. I am running oil that is at least a grade heavier than spec'ed for my truck and thus far, even nearing 15K miles on a P1 filter, the engine seldom reaches the DP where bypass begins. When it does, it involves one of the following situations; cold start and high revs; extremely high revs (5000+) with oil below 150F. If I drive sedately during warmup I stay well below bypass and if I wait until the oil is past 170F, I can rev all I want (not that I want to often...only for tests!). So my testing seems to confirm what I was told that bypass events are "infrequent."
b) Bypass is not an open or shut event. Even during a bypass event, some, if not most, of the oil is still going thru the filter media. When oil is flowing, most of the contaminants, certainly the lighter ones, are stuck to the media with the oil flow. This means they are not likely to be pushed thru the bypass. Those that are are very small in number. Say the bypass spec is 16 psi. A single number spec means that the bypass is fully open at that pressure. Purolator is a bit more accurate and gives a range, 9-16 psi for my filter, which means that filter may crack at 9 psi and be fully open at 16 psi differential pressure. Again I refer to my tests: I am not seeing much more than DP when I am in that ballpark and even completely ignoring propriety by flooring the engine and revving to 4500 with 45F oil, I have no more than 2-4 psi above the cracking pressure meaning the valve is not open very much.
c) Most modern engines are running pretty clean. Another factoid I gleaned is that most filters are nowhere near full at the time of a change.. even those run to 7.5-10K. That testifies to engines running pretty clean. The point here is that the contamination level in the oil is low, so whatever does get past the filter in a moment (a second long perhaps) will not be much.
d) Not all filters in a family are base or dome bypass. In fact, I think MC is the only line that has the base end valve feature on the majority of it's part numbers.... certainly those destined for OE Ford approvals. If you look at pics of M1 or RP filters, you see only a small percentage of part numbers that have the base end feature.
e) Two engineers told me that the base end bypass valve design commonly being used (looks like the same design on everything MC) is "problematic." The farthest they would go down that road is that they saw a higher number of failures with them than with the more common and conventional design used on the dome end. Not sure what that all means.
Bottom line, is a base end bypass is "better?" Perhaps so when looked at as a single design element but that's not all there is. In the context of all the other stuff going on with lube filtration, there may be many more important features so I wouldn't recommend the location of the valve to be a deal maker or a deal breaker in choosing a filter.
Finally, all this is conditional. If you run 15W40 in an engine designed for 5W20 and do so in a winter climate, then start you engine and race off to work... your engine will see many more bypass events than most everyone else. Ditto for guys who race and go from near idle to 8,000 rpm in a flash or guys who run a filter too long, have a high contamination rate (often and commonly due to inefficient air filtration). If you use the right grade of oil for the climate and according to mfr viscosity spec, go easy on the engine as the oil warms up, aren't a hotrodder, you should see few, if any, bypass events.