I'm kind of doing a
at people saying the only negatives of CBS are things like that they give bad advice. I'm not as familiar with them as others, but I know there's a lot more to be said on them than that. Here's my best attempt at impartiality.
* CBS probably has some of the nicest canned graphics and appearance available. While you can do pretty much the same on other sites, it may be easier to do on CBS. They have niftier stuff you can just select and it works. I don't know that they have any better or worse live scoring than anyone else. It seems a constant that the first week of the season most FF sites have to redistribute leagues to balance server loads, but any competent site seems to get it right quickly and I don't recall any particular #####ing about that in regards to any site after the first week.
The biggest disadvantage of CBS is that it costs $150 a league while other premium sites cost from $60-$80 a league. To me that has always been the dealbreaker since I didn't think the graphics were worth more than twice the price, and I felt they were also worse in other areas, which leads me to what I'd say is their second biggest disadvantage. Customer support. If you're going to make a vanilla, cookie-cutter league (to mix metaphors), maybe that won't be an issue. But the impression that one gets on here is that they don't have very responsive or personalized support, you're more likely to get a FAQ email that may have nothing to do with your issue, than get someone to address it right away. My friends on ESPN said the same thing about support.
I also don't think CBS has as much functionality/flexibility as other sites. They can support a lot of league types, but I'm not sure that they have as many options as the other sites out there. I think they put more of their emphasis into being part of CBS and having access to CBS content, while other sites try to win clients by being feature rich.
* MFL's biggest advantages would include flexibility, as I think they probably have more functionality than CBS. They also partner with other sites so that you have the option of going out and using FF industry best software if MFL doesn't own it, but be able to transfer the results into MFL easily. Fantasyauctioneer.com auctioneer is a good example of that... they have what many consider to be some of the best auction tools out there, and you can do auctions there and have them transferred into MFL without having to do any work.
Customer support is another of their plusses. I've never had it take more than a few hours to get a response via email and it's always been an actual typed up mail that addressed my issue. But I don't even use email for support anymore as they have staff monitoring the support forum and you normally get an answer within an hour.
If you're any kind of web designer really the sky is the limit on what you can do. And even if you're not, it isn't hard to come up with some that looks good. They've also put more effort into appearance of late with some prepackaged skins that look pretty good that you can just select and it sets everything up for you. And if there is some glitzy graphics thing on another site that you just have to have, there are sites where people will custom code such a thing up for you for a small fee. Some of the developers of mfladdons.com are in the Shark Pool here I know. Now if you do feel the need to go out and supplement things with code you pay someone else for, it is going to offset the fact you can get a league for less than half the cost of a CBS. But I've never felt a need to pay for such things (and there is some pretty cool stuff available as freeware even), and even if I did I think we'd still come out ahead.
I'll also give a kudos to MFL for how responsive they are to requests for new functionality. I think I've probably requested about 15 things, some minor like giving more lines in the news summary, to major ones like modifying how they do acceptance of trades and blind bidding. They've probably done 10 of them (and I expect another 2-3 will be done this next offseason as I just put them in the middle of this year).
With the extra flexibility comes the biggest detriment of MFL. If you want a shrink wrap website it's not going to look as great, and the extra functionality they have will of course take a little more set up if you want to use it.
* RTS and others I don't think I've had enough experience on them to be able to fairly say very much. I have a generally good impression of RTS from what I hear about it, and it also seems to fall into the costs-half-as-much-as-CBS, but I couldn't make a feature-by-feature comparison for example... whereas I at least had used CBS recently enough to have an idea what's out there for them. Yahoo I don't think is worth mentioning in comparison. It is MUCH MUCH MUCH less than the premium sites in terms of what you can do. You don't come anywhere near what is base functionality on other sites unless you buy something like Stat Tracker. And even with that, it's less than what you get on other sites, and the cost of a league of 12 buying Stat Tracker is more than the cost of just having got the league on a site like MFL or RTS in the first place.