The TTB-vs.-SA debate is never ending, take everyone's opinion, and decide which is best for you.
Well, to give my opinion on the points you made (more for everyone to ponder
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ttb has 1 more u-joint than a SA, i.e. one more "weak point" (the passenger side axle literally has 2 u-joints on it)
Yes, there is a 3rd u-joint on it, however I don't see that one as a "weak point" because it rarely, if ever sees the same operating angle as the steering u-joints, therefore it should be less likely to fail (unless of course it gets bound up because of too much suspension droop... Clearancing the yoke if needed or installing limit straps/cable(s) would eliminate that possibility. Simple as giving the axle a half-turn by hand with the suspension at droop to check).
i've also never seen a guy twist and destroy the entire housing of a solid D44 front. but a search will yield a handful of guys who have mangled their TTB housings, not because the carrier or gears failed, and not beause the u-joints failed, but because the way a TTB front end is, it is much more vulnerable to catastrophic impacts
I have. Both SA and TTBs.
In numerous TTB cases I've seen, it was because someone was driving around on it without the pinch bolt installed behind the diff. Ford (Dana?) put that bolt there for a reason.
Cases with SAs were because someone (ignorantly) welded radius arms directly to the housing during their SAS (broke the welds and spun the tube in the pumpkin), another dude tore a link bracket off and the tube cracked & buckled right at that spot.
I've seen
BOTH destroyed by high-speed impacts into rocks, tree stumps, etc., and by ruthless jumping w/o the proper equipment.
Point being, ANY axle can be destroyed under the right conditions/abuse.
and third, the more ttb is made to flex, the more you need to not only modify shcks, springs, and links such radius arms (as you would an sas) but you also need to modify the diff itself to improve flex, this is done by opening up the "window" that the axle passes through, allowing it to move around more inside the housing. that's right, in order to improve flex, you need to take an axle that already has additonal weak points, and cut material out of it.
Around the window is not a weak point. Weak point is on the backside where the beam opens to a C-channel section (there's a few reports floating around of cracks right where the weld ends). Box it up with plate. Done.
Ok, so you still think the window is weak... Then plate the beam above & below it. If that provides you comfort, great! Certainly it doesn't harm anything.
that doesn't even address the need to "cut and turn" the housing
Cut & turn is only desirable if you're doing the jumping/prerunning thing. It's not actually "needed" anywhere (and does have a couple drawbacks as well).
whereas no integral modifications are needed on an SA to facilitate flex, it is all done with shocks, springs, and links,
As is also the case on a TTB, the only exception being the widening the beam window you already mentioned (ok alright, and make sure the p-side radius arm bolts don't protrude too far into the beam).
TTB can be really awesome. but in my opinion when compared to a DANA 44 SA, the TTB has inherent (sp?) weak points, and pitfalls that outweigh whatever benefits TTB has.
Everyone does have an opinion (and I respect that). Solid axles also have their place for sure. Certainly they are more readily accepted as "something decent"...
My personal observation is there will always a number of people that won't be happy with the TTB even if it were to give them exactly 0 problems. Perhaps they relate easier to the SA since it's just a simple straight beam with a wheel at each end... Or maybe they did have a (usually fixable) issue but then somebody else came along and said it's junk for "that reason" and they don't want to think about it any further. Whatever the case, a SA is the only thing they're willing to consider, which is fine. Certainly it works, and very well at that, provided the swap is done correctly.
For hard-core guys, the SA is their only choice (without possibly breaking into $five figures anyway) as axles like the venerable D60 only came in a SA version.
For myself and many others however, the TTB works perfectly fine, and to me it makes no difference how goofy it might look when it twists in it's own way offroad. As long as it gets it done with no fanfare, doesn't affect my tires negatively, is reliable, and is low-cost to maintain, I couldn't care less what kind of setup it is.
Lately I've been bombing it around at faster speeds with this vast desert fairly close by me. A SA is gonna have a tougher time with this type of use... TTB (or any IFS for that matter) takes speed a lot better due to lower unsprung weight. With it also capable of the same slow-speed-ability as a SA when set up right, what's to lose?
BUT for a dd/weekend wheeler the ttb should be fine.
My rig probably does fit the "DD/weekend-wheeler" category somewhat better than it does "hardcore-extreme", as it still spends time on the street (and needs to be comfortable on long trips). I also like to do the traveling-while-wheeling/camping thing (seems the latest trendy word for this is "overlanding", though I prefer to simply call it camping). That doesn't stop me from hitting a decent trail like Rubicon though, and it handles it just fine (guys I wheel with often marvel at the ttb, they don't expect to see anything but a solid axle do what it does on some of the trails we go lol).
Finally, yes there are pitfalls with the TTB... Almost all of them are there because of obsolete suspension lift designs (the too-short drop pitman arm screwing the steering linkage angle is by far & large the biggest one). Learn a little about it and there should be no unseen pitfalls. TRS is probably the best resource on the web for this.
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