Your Bobcat trailer will be more than heavy duty enough, a typical skidsteer is going to weigh twice as much as a lightweight snowcat. The problem you will face with the Bobcat trailer is the width between the wheel wells. A Snow Trac ST4 is going to be 6'2" wide so you need at least 6'6" between the wheel wells, my car hauler has about 6'10" between the wheel wells. Most brands of snowcats will NOT fit in between the wheel wells of a typical trailer, most require a bed over the wheels so keep that in consideration when you are shopping for a snow cat.
As for slush, it is basically a non-issue, at least for a Snow Trac and I presume for every other brand (I own a Snow Trac so it is what I have most experience with). These things will manage any loose material from sand to gravel to tall grass to snow. I've never had a problem with slushy conditions. Ground clearance on most brands of snowcats is going to be roughly 12" give or take a couple.
As for price, it varies but a decent used one will start about $5000 and run up to $15,000 (for an older model). Depending on condition!!! It it easy to pay more, hard to find them for less. Prices have been going up over the past few years as people find out how useful these things really are, and as sled prices go up. (actually its getting pretty hard to find a good one for under $8000 but there are some deals if you really search for them) A new one will start about $75,000 and go up to $400,000 depending on features/design.
I can't say what is "best" for someone else, but I know what is best for me. Each snowcat will have somewhat different characteristics, each will have differing maintenance needs, etc. Figure out what your needs are and find a snowcat that fits your needs. If your trailer is your limiting factor, that alone will knock out a bunch of different models unless you are willing to consider buying a new trailer too.