I need to have a plate. so based on all of the above am I better of with AL or SS plate
The proper answer is,
it depends on you, and your inherent buoyancy characteristics (and, to a certain extent, your preferences for exposure protection).
The safe answer is: the AL plate. Or, actually, one of the lighter SS plates that are now being sold in place of AL (e.g.
https://www.divegearexpress.com/dive-rite-xt-lite-ss-backplate). It is the safe answer because you can always add a small amount of weight if you are underweighted with a light plate, while it is hard to take weight off if you are overweighted with a standard SS plate when wearing no additional weight. You could also consider a Kydex plate form Deep Sea Supply.
But, there are more than a few divers in this world who are not overweighted in warm water with a SS plate, and you may be one of them (I am). When I dive warm salt water, I wear a 1 mm full exposure suit. With an AL cylinder, and a SS plate, I still add 4 lbs of weight. So my inherent buoyancy characteristics allow me to use a SS plate for warm water diving. Some people are inherently less positive, and for them, even an AL plate is enough to let them dive without added weight. Frankly, many divers end up with both. You need to assess your inherent buoyancy, in the 1-2 exposure suit (which I presume is the thinnest you will wear, without a floaty / fabric BCD, in fresh water. If you are negatively buoyant, you may not want want a steel plate. If you are positive, then steel may be a better choice. If you were using steel cylinders, then all bets are off and you might lean toward AL / light SS plates.
As for brands, I won't offer a suggestion. I have a torso that allows me to use a 'standard' length plate (~15 1/2") without difficulty - I have several Dive Rite SS plates, and both SS and AL OMS plates, all of which work fine - for ME. You can get longer, or shorter plates if your physiology requires that, you may hear from some that the angle of plate curvature makes a substantial difference for them, etc. I am probably not sufficiently discerning, or skilled enough, to make such an assessment.