I have a sailor as well as classic and soft RM packers!
Since the RMs are made of a nicer material, I'm going to generalise with overall texture, because it's not quite as simple as the firmness itself.
I would always recommend the soft over the classic RM because it feels more like skin. In the case of comparing it to the Sailor, I think it's closer than the classic, but only just barely. I've heard the soft tends to change texture as it gets older and now that I'm looking into it, I think that's true. Mine's nearly a year old I believe, and the different between the two textures used to be greater. I would hesitantly say that initially, a classic would be more similar because of the sailor's core, but long term the soft is closer. The way a soft squishes is different than the classic, and I think the soft is closer to the sailor in that regard.
As for the weight, BOTH the classic and soft are significantly heavier than the sailor. Whether it makes a difference or not depends on how you pack it. The soft cannot be packed in a harness- ie the texture is prone to ripping if you do. The classic is one of my most durable packers, second only to a pack-n-play from Freetom, so could be in a harness. I definitely felt the soft was quite delicate when I first got it (they instruct you not to handle it by the shaft to protect it), but now it feels much more durable and I am comfortable being a little rougher with it, though I still won't risk using it in a harness. If you pack it in, say, briefs or a jockstrap, weight doesn't much matter. I personally like the weight because it reminds me something is there as opposed to feeling disconnected from it.
If you need to use a harness, I would recommend the classic, but otherwise, I would recommend the soft, as it does get less delicate over time.
