I'd suggest that if approach angle is causing a problem for a D40 with an ARB bar, then that is one awfully big brick wall people are trying to climb.
Honestly, look at the vehicle from the side. Draw a line from the bottom of the front wheels to the lowest, most exposed part of the bulbar. That is your approach angle.
If its a big jump up, then the tail will never drag through - the departure angle is too small to get up. If its a short step-over, then wheelbase is too long and the overall height too low - the ramp over is insufficient.
I'd really love to see some pics of these climbs which are supposedly causing people such an approach angle issue.
With bars, both ARB and TJM are quality items. The Ironman bar with bolt on hoops is a faster waiting to happen. The fully welded one, have seen some really bad quality manufacture on them so personally wouldn't touch them.
It always used to be ARB and TJM putting out mostly the best quality gear, and I think that now TJM are ramping up again, they will become a real force in the industry once more and rightfully so.
What it really comes down to out of those two in my opinion is cosmetic choice.