Canon 135mm f/2 L vs Samyang 135mm 1.8 vs Viltrox 135mm 1.8 for A7iii

Hi everyone,

As the title suggests, I'm looking to get myself a 135mm prime lens. Confused with the above 3 options.

I prefer sharpness, AF and light weight.

I have below options in terms of price

Canon used + adapter - Rs. 45000 ~ $510 Viltrox new - Rs. 75000 ~ $850 Samyang - Rs. 56000 ~ $630

From what I've seen is Viltrox is the sharpest and heaviest. Samyang and canons are much lighter

I know that all 3 lenses might be equally sharp for A7iii but I might want to upgrade to a a7r4 later.

Also can anyone share their experience with mc11 adapter and canon 135 - how's the AF?