Regarding Vue without Poser figures, well it works so much better. Poser figures are memory intensive due to the amount of morphs & texture sizes. Vue can choke if too much is loaded. More RAM is definitely recommended if you can.
If you are doing mainly landscape work in Vue you shouldn't have too many problems with memory issues. The only thing you may come across is render times when using Global Radiosity, soft shadows etc & high render settings. It looks beautiful but render times can be slow, but is really worth it!