Hi Gerry,
I have a number of ZWO cameras, including the 224MC but not the 662MC. The 224MC remains an excellent planetary camera, though it is of an earlier generation than the 662MC.
The frame rate quote is always a bit confusing, because it is highly dependent on sensor dimensions and pixel count. Because of the volume of data flowing from a larger sensor, it will have a lower fps than a small sensor, if you were imaging over the whole sensor. In other words, it is a quote for what the max fps would be if you were using the whole sensor. The sensor on the 662 is similar in size to the 224 but the pixels are smaller, so it ends up with nearly twice as many pixels as the 224. This contributes a lot to the lower max fps of the 662. In actual practice the planet will occupy only a small part of the sensor so this max fps will not apply.
Now, although you will be imaging the planets generally using only a small part of the sensor (using something like "Region of Interest" in Firecapture), one of the limiting steps when you are starting out is trying to land the planet on the sensor, particularly when you start using Barlows etc with a dimmer image and a smaller field of view. This can be very frustrating, and a larger sensor can be a help. However, the 662's sensor is slightly smaller in area than the 224, so there is no big difference there.
But a better option might be the 585MC - the latest and improved version of the 485MC (which I have), that has an enormous sensor (though of course it is more expensive than either) - much easier tto find the planet, and you can use the big sensor for capturing wide screen vistas of Jupiter or Saturn and their moons.
Here is a quick comparison:
224MC; sensor size (rounded) 5 x 4 mm; 1.2 MP; $199
662MC; sensor size 6 x 3 mm; 2.1 MP; $249
585MC; sensor size 11 x 6 mm; 8.3MP; $399
You can do a more detailed comparison on the ZWO website here.
Another thing to consider:- you want to optimize your f value at around 5 times your pixel size. A size around 2.9 microns (the 585 and the 662) gives 5 x 2.9 = 14.5 which is close to the native f10 of your scope - probably close if you use an ADC. The 224 is 3.75 microns meaning you would need to use a Barlow around 2X to optimize your sampling.
You probably know you will need an IR-cut or luminance filter with these cameras to improve colour balance. Make sure you check out the FAQs at the top of the section - a wealth of useful advice there.
But I would emphasise that there are no bad options above! Just marginal pluses and minuses. Most of the time you won't be using the whole sensor and the max fps is a bit of a red herring. And your major quality determinant will be good seeing, good focusing, and good collimation, rather than camera!
Regards
Mark