I am considering either the Express Tech with the 30# wing or an aluminium backplate with 30# wing and hogarthian harness. I would appreciate any input as to which way to go.
I have both, although in actuality I have an Express Tech plate, which I then rigged with web harness - IOW, I DO NOT have the 'deluxe' harness. I would not recommend the ET Deluxe as sold, because of the harness, and the wing style (horseshoe).
Of the two, I find an AL plate to be a little more useful, as I need added weight, even when diving in warm (salt) water with a 1mm exposure suit. In fact, I prefer a steel plate to the AL plate for single cylinder diving, because of the weight of the plate.
The answer for YOU depends on your buoyancy characteristics and exposure suit preferences. If you are inherently negatively buoyant, then the ET might be a good option. If you are 'floaty', a metal plate is possibly a better choice. Yes, you can add weight if needed. But, why bother, if by buying a metal plate, you are optimally weighted without it? Since you specifically mention an AL plate, why did you choose that? Have you already checked your buoyancy with an AL plate, and your usual exposure suit and cylinder, and found that to be the best weighting? If so, go with it. If you are still light with that configuration, definitely don't go with the ET, rather consider a steel plate. If you are heavy with the AL plate, consider the ET.