You can discuss steel and alloys for a week but it comes down to personal preference and what you are wanting to do with your knife.
I personally need a steel that will be durable with a lasting edge but that can be sharpened in the field as well. You can heat treat many alloys that are in the mid 60s for hardness but that won't do you much good when it comes to trying to sharpen a knife in the woods with stones. So even though you can obtain a rockwell hardness of 66 you need to temper that knife evenly to around 58-59. This can be achieved by using an oven and using vermiculite to make sure your temp stays more consistent through the 2 tempers at 2 hours each. I personally always do a snap temper at 300 degrees immediately after the heat treat to relieve any stress in the steel.
I use mostly all high carbon alloys and alloys such as 1095 L6 O1 52100 1084 1080 all of these will get you in the mid 60s but again they need to be tempered.
Again because I am forging frontier style knives I want my knives to be at a hardness customers can put an edge back on. I could get a 63-65 rockwell hardness and get an edge because I have a belt grinder to do it easily but with stones its a different story. Anyway I hope this information helps on picking out a steel.