I have both.
In my den, I have a HTiB from Sony that is acceptable. I use it primarily to watch TV or Netflix, and my Xbox is hooked up to it for the occasional DVD if need be. All audio is routed through it (bypassing the TV) so it is on whenever the TV is on. I have a Harmony remote that controls all the devices in that room. It isn't capable of DTS or TrueHD decoding on-board, but it will do 5.1 Dolby Digital or pcm if the transmitting device does all the decoding (all blu-ray players are required to have on-board decoders per spec. So no pretty little blue light on the receiver if I'm listening to HD content, but it's technically the same sound). The speakers are impedance matched to the receiver, so if I ever need to replace one it must be the same oddball impedance as the receiver.
In my living room, I have an Onkyo Receiver (the Onkyo TX-NR609 to be exact). It is a 7.1 internet capable receiver, but I only have 5 speakers and a sub hooked up to it. This thing blows the pants off the Sony HTiB in the den, and it cost about the same price (maybe $100 more). I bought the receiver in a combo with Onkyo speakers, and if I ever want I can easily upgrade each speaker one/two at a time. It has every connection you can shake a stick at, and also does video processing so I can hook my Wii up to it (or even my SNES/N64) with old school component or composite cables, and it will translate to HDMI on the fly. It also accepts 5 HDMI cables and will do straight pass-thru to the monitor (in my case, a projector). It's also got Pandora/SiriusXM and DLNA, which is nice, but I have a computer hooked up to it so not really necessary.
So as others have said, it depends on what you are looking for. If you want power and options, go with a receiver. If you have other devices that take care of all of your needs already and you just need sound, and don't think you'll ever upgrade the components, go with HTiB. I also suggest going to AVSforum and looking in their HTiB subforum for advice. I'm a veteran over there.