Is it advisable to freeze tomatoes

When tomatoes are cooked (which I assume you plan on doing for canning or after freezing) the skins become tough and usually detach from the tomato. Since you usually don't mind this, you shouldn't mind it with canned tomatoes either, but many people do - even when pureed the texture is different.

When freezing you can freeze whole and the skin should come off easily when thawed.

One way to get around the texture issue would be to puree the tomatoes and then force them through a food mill, which will help to remove tough bits - do this either before canning or after freezing.

Tomato puree is concentrated tomato. So where it is called for in conjunction with other tomato products, be they fresh or tinned, it is an attempt to increase the tomato flavour/presence in the dish without increasing the bulk or water inherent in less concentrated products.

Additionally the flavour of puree, having gone through a reduction process is somewhat different, more intense and rich than straight tomatoes.

Indeed, canned tomatoes tend to be surrounded with juice that is more reduced than would occur naturally. Which is part of why they are used against fresh tomatoes.