I got some experience last year mixing HDV and AVC/MP4 video. I bought one of these relatively cheap HD camcorders, the Sanyo Xacti FH1, mainly to save wear on my Sony HDV camera. I was shooting 2-3 soccer matches a week, and really did want to mess around with the tapeless workflow without risking too much cash.
The camera turned out to be surprisingly good. It actually does 1080/60p video, which is handy for sports, or for that matter, anything that might go to both web and DVD/BD. It's far from perfect, and while the video is great for a consumer camera, there's not much use for the audio. Nearly all controls are on-screen (this is even smaller than the consumer Canon SDHC models), but surprisingly, it has full manual exposure control. And a fairly big sensor -- 1/2.5", 8 Mpixel.. so it doesn't have Bayer pattern fringing like older single-chip consumer models do.
And it's proved a useful enough B or C camera... easy to hide, too. And I've found I can match color between this and the HDVs, if the Sanyo's set up properly for the shoot.
The AVC stuff isn't all bad. This is technically not AVCHD... it's the same basic idea, but it uses all MPEG-4 stuff (AVC, AAC, and MP4 file wrapper) rather than the BD-derived stuff in AVCHD (eg, AC-3 and the MPEG-2 TS file wrapper). On my Q9550 PC, basic editing is doable, directly on the AVC files in Vegas Pro 9. For anything complex, though, I'm probably going to convert to Cineform.
One downside with this camera... there's a bug in their MP4 container creation of some kind, maybe related to time codes, that causes Vegas to sometimes crash. I can re-mux the MP4 and AAC to fix it, or just convert to Cineform.
Anyway, the plus side of SDHC-cards versus tape convinced me. I recently upgraded the Sony HVR-A1 to a Panasonic AG-HMC40. It's all good.
Comparing the Sony FX-7 wasn't really in my sights, because I was specifically looking to go tapeless, as well as upgrade that A1. For direct comparison, you can trust that the Sony's going to deliver at least a better low-light performance. It's using 1/4" sensors too, but they're half resolution with offset, thus, a bit more light gathering. With that said, they did a nice job on the HMC40's sensors... I crank the gain up to 12dB-18dB and it still looks like video. I'd never go close to that on a CCD camera, or even the older CMOS-based A1. But the CMOS technology has been advancing fast, particularly in the areas of noise management (unlike CCD, the CMOS tech these days can actually cancel out any fixed noise, like dark current related issues... it's only the random noise that remains an issue).
I was also a bit skeptical about AVC in the past. The CODEC itself is great.. you should get at least twice the coding efficiency of MPEG-2, given the right encoder. But it took a good 10 years before pretty much every MPEG-2 encoder looked good. AVC's been advancing, but change that to "realtime AVC on a 5W camcoder", and you'd have to wonder. This started to change last year... even on the consumer models, like the Sanyo and the Canons, they were starting to see video that looked better than HDV. This is pretty much what you expect with a 2009-2010 AVC model. Conditions vary, but I believe the HMC40 is cleaner than either of my HDV models on most input.
