Just to join the echo chamber - it's very subjective.

Like others have said - I can sleep fine in the front of the plane, I can nap (but not really properly 'sleep') in WTP but I really struggle to in WT. For a night flight, that's the main thing for me - and it's a combination of the 'better' seat and quieter cabin, and sitting at the very back would mean I arrive grumpy, mess up my sleep pattern and lose most of a day trying to reset it. However some people do somehow sleep at the back of the plane, which is a talent I somewhat envy.

For a daytime flight, WTP's still more comfortable and you get a better main course, but I can see why you might not want to pay more than you need to especially on a shorter longhaul.

I believe the saying is "happy wife, happy life". If the wife is generally not too bothered about such things, will comfortably fit in the WT seat and money is tight though, it might be just as well to spend it getting her a decent meal and a massage at the hotel instead....