All this stuff has been done to death on pilot forums many times.
There isn't any way to arrive at an airfield which is inherently safe. Some offer you a better view of the existing traffic than others; that's all.
IMHO, the OHJ is one of the worst because if several planes arrive together (which is likely, because at many airfields it is only when ATC can't cope that the OHJ is requested) they will end up orbiting all at 2000ft and any one of them can't possibly be visual with all the others. The procedure relies on each one seeing traffic in front - they can't see what's behind. But different pilots have different views of the "correct" diameter of the orbit.
With a straight in, one is flying straight ahead, thus has a low cockpit workload, and is in a good position to have a good look around for other traffic.
It's true that one cannot join a tightly packed circuit from a straight in, but one can't join a tightly packed circuit from any other arrival method, either
A straight in join also offers the potential, for anyone with TCAS, and assuming everybody is transponding, to check for traffic in a rather more robust way.
I think that many pilots are suspicious of the OHJ in that it is regarded as the "goode olde English proper RAF way" and gets over-used, sometimes deliberately to make life hard. I recall going regularly to Panshanger a few years ago, and there was some masochist (GA is full of these types) on the radio, a PPL instructor I believe, who would firmly request (even though he had no legal right to do this) an OHJ, for what was a RH circuit (i.e. the most difficult combination to visualise), and I am sure he just sat there and laughed his head off at all the pilots who did the wrong entry etc. With the proximity of Luton this probably resulted in a few pilots shooting off in the wrong direction...