I've looked at this relatively recently, although not in any really analytical way. What I've done suits me, but others almost certainly have different requirements. Certainly there are things I'd
like to be able to do, but can't at present.
I have some hosted online space of "my own" here in Australia. However, that's for a bunch of mostly non-photographic stuff, and is way too expensive to fill up with photos I put online for various reasons.
I looked around for some space where I could store photos "for free" in fairly large quantity (at low resolution, though - mostly 640 pixels as the longest dimension). All this needs to be is a holding space, so I can link to the photos from posts elsewhere. I thought my only requirements were free space in sufficient quantity, and the ability to upload a batch of photos almost as easily as a single photo. While hardly exhaustive, my looking around took me to
flickr as being suitable for my purposes. I did not look at, and have no real interest in, the "community" aspects of the site (photo critiques, "friends" etc.) as the general standard of photos uploaded to flickr (my own included) has a pretty poor "keeper" to "snapshot" ratio.
While I'm not really into it,
deviantArt seems better for showcasing your best work, seeing others' best work and so on, as its self-consciously an "Art" site (whether you agree in practice, or not). dA doesn't allow you to link to photos stored there, from other sites, so its pretty useless for that. (dA is also about more than just photography, though its my only interest there.)
And that's where I sit - except that I upgraded my flickr account to a paid one. This was simply to be allowed to group my photos into sets (or more than about 3 of 'em), so I could direct people to just one set to see the photos they are/were interested in. This was for a couple of Aussie Rules football matches I shot, where I could upload photos for people in "our" team to look at, and for them to then e-mail me regarding any prints they might want. While there are other ways I could have done this (for free on flickr, or elsewhere) it was easy for me to do it, and not expensive (I recall about US$30 for a paid membership).
Of course what I'd really like for that kind of application is something like Photobox (I think) in the UK where you can put up low-res shots (for people to see) and have people select and buy prints at whatever sizes and prices you set, with Photobox printing from a not-downloadable high-res version, charging their base rates for the printing, shipping etc. and paying the remainder of your price to your account. There's nothing like that here in Oz, or from anyone who will even ship prints here. (Perhaps a business opportunity, someone?)
I've probably gone on too much here, about far too little. But for what its worth, its what I'm doing.
...Mike
http://www.flickr.com/photos/mfunnell
http://mfunnell.deviantart.com/gallery/