The equivalent tire would be a LT285/75R16 or LT285/70R17. Either would be fine so it comes down to cost and personal preference. New trucks use 17" tires but I don't think 16" tires are going away any time soon.
NOT to be argumentative, but the equivalent of the 33x12. 50x16. 5, is actually a 305/75R16... ... The 285/75R16 is spec'd to replace the 33x10. 50. A 255/85R16 is a 33x9. 00.....
I would think it depends on what wheels you want. If you're going to an 8 or 10 inch wide wheel in 16, I'd go with the 305/75R16. More air volume equals greater ride, combined with the width, which gives more road surface for handling, wear, and some added stability when loaded.
The 285/75R16s are the most common upgrade tire in the 16" rim size, and typically are 10-25% cheaper than their 17" equivalents, and more readily found, and usually easier to find in 10ply versions than their other 16" counterparts. The cost of 16" wheels is relatively low and there is a surplus of them available on the market. The 285s, again, would fit factory wheels more readily than the 305s, according to most tire manufacturer's fitment guides.
The 17" wheel size is currently more popular on newer trucks, mostly due to design changes in brake systems and clearance concerns. While I find nothing wrong with the wheel size, there are fewer actual tires available from as many manufacturers, although I couldn't exactly call it a shortage of selection... ..... The prices of 17" wheels and tires trends to be higher than 16", mostly, in my opinion, due to the higher demand of newer trucks and a somewhat smaller selection of available choices.
If you find a cheap set of whatever wheels, perhaps with tires, that would probably sway my choice, but otherwise, I'd go with the 16".....
