I'm a big fan of podcast hosting services like Blubrry, Libsyn, Buzzsprout and others like them. I am less of a fan of posting podcast episodes on Soundcloud and YouTube. To me, if you even consider these options, you need a great reason. Even then, I'd ask you to think twice.
Granted, it's easy and cheap to post your episodes on Soundcloud. However, you miss out on the analytics and other services that full service hosts can provide you. I also don't tend to see Soundcloud podcasts with huge followings, and I have to wonder how challenging it is to grow it. This is going to be especially challenging if it's one of the only places you can get the show (versus iTunes, Stitcher Radio, etc).
Also, there are constant rumors about shutdowns and acquisitions of Soundcloud. If that happens, who knows what changes could take place. How will it affect your show, the distribution or even the ownership of the content?
As for YouTube, if you have your audio podcast posted there and on iTunes...I'd like to know why. I would think the ideal scenario is to grow subscribers on iTunes. If that is true, putting the exact same show on YouTube is splitting that audience up. Some get it on iTunes...others hit YouTube. How do you quantify those stats? At least if you're using a hosting service like Libsyn, your feed can be sent to several podcast hubs and they all get those downloads counted.
Obviously, if you do a video podcast, that's different. Although, I have reservations there as well. If the "video" podcast is just a visual of you recording audio...I don't get why someone would actually WATCH it all at one time. What's engaging about that? A lot of people don't have that kind of attention span, and I think many people are inclined to just minimize it and listen. If that's the case...why have it on a video service at all.
Plus, you really don't see video podcasts frequently hitting the top podcast lists on iTunes.
Now, I'm not saying these services are totally useless when it comes to your podcast. I just don't think you need to post full episodes on them. Instead, post interview clips or memorable moments from your show. Tag the end of the audio file with a pitch to GET MORE at your podcast website.
On YouTube, you can do even more. If you upload a cut from the show that features a specific topic, you can keyword the title and description for people to find it. Plus, you can post links to your website and/or where to subscribe to the show.
So, instead of giving up everything, make YouTube and Soundcloud a place where you feature the BEST of your show, and and tool that can entice people to get your full episodes. It makes a lot more sense while also being a lot less risky and counter-productive.