Here are some questions:
What are the positive points to the 700 verses a smaller Kodiak? Honestly . . . for most folks I suspect a 400-500 cc machine is fine for most uses, especially if someone is using it for light work or trail riding. I went from a Honda Foreman450 (although the actual engine was something like 420cc) and it did most everything I needed perfectly fine (i.e. haul firewood, plow the driveway, trail ride, etc.), but to be frank I wanted just a little more power and speed (not that I often use it . . . but being a typical guy one always wants "moar pow-ah".
Should my new ATV be a Yamaha? It' really up to you. I'm probably the wrong guy to ask since I'm 48 and have only owned three ATVs -- a Honda TRX300, the aforementioned Foreman 450S and now the Kodiak 700. I find that most ATVs have stepped up things pretty well in terms of reliability and features, but there are still some differences and it's all on what you most value. For example, Hondas have always been and will most likely always will be near bullet proof when it comes to reliability . . . the trade off being they're expensive, they don't tend to have a lot of big power machines (well one . . . and that one is geared more for trail riding) and they either don't have as many features as other makes and models or you can get those features at a premium price. I find Polaris ATVs to be a bargain in terms of price when coupled with features and their ride is highly regarded . . . but I also see more folks have break downs with Polaris ATVs. I could go on . . . but I think you get the idea. I went with Yamaha since they had exactly what I wanted -- a larger engine ATV with the features I wanted (IRS, power steering, automatic), an ATV geared expressly for work and play (I use my ATV for work as much as I do for play) and at a price that was quite attractive . . . AND most folks (users and experts) rate Yamahas highly when it comes to reliability.
Should I get an 18 rather than a 19, there seem to be a bunch of 18s around. If you're in no rush and not picky you may be able to get a hold over at a good deal. I waited for a bit, priced what I wanted at the various dealerships in the State and was able to get a new hold-over at a good price (the bonus being it was in a color I liked and came with alloy wheels). The drawback was it was an older model and at the time it meant it did not come with the push button locking differential . . . which to me was not something I have needed in the past . . . others find a locking diff to be essential . . . it comes down to what you want and/or need.
Anyone want to offer some of your own perspective, that would be great.