The current fashion for large pots planted with a variety of things - in what I call the cornucopia style - seems to me to be out of scale for normal people. You know the sort of thing, because it appears on the terraces of grand country houses and in the pages of decorators' magazines. There is a huge terracotta pot, half the height of a man and 2ft across with a spikey plant at its centre, five different geraniums to trail down the sides, as well as a few daisies, some scented heliotrope and a cascade of grey helichrysum. It is more of a flower arrangement than a garden; when it works it looks terrific, but such mixed plantings are demanding and can look daunting in the wrong setting. The advantage of cramming all your plants into one container is that they are likely to need less watering, but I think if you can vary the heights of pots and make up groups from smaller pieces it is visually more successful. You have the same variety of plants and they often do better as a result.
If variety is not your style, there is another option that is less demanding for the gardener. Find a plant you like - it might be tulips in spring, followed perhaps by carnations or pansies in summer, or you could choose something permanent such as lavender. Put them into identical pots and set them out in a row. This sort of thing looks good on low walls or up the steps of a basement area. Or you might have a collection of ferns in a dark, damp place in pots of different sizes. Having collections of one kind of plant that you particularly enjoy means that you can treat them all the same, which makes for less work.
Window boxes and troughs can be planted cornucopia fashion or restricted to fewer plants. If you prefer geraniums, daisies and lobelias mixed, to a boxful of geraniums on their own, then go for that. Either will do well, it just depends on your style and that of the house they adorn.
The containers you choose will make quite a difference to the overall effect and also to the plants they support. For example, wooden tubs are perhaps better in the country than painted Versailles cases. Modern houses can have pots in high-tech materials, but older buildings will seem happier with traditional clay or stone. Container gardening is so popular that there will be something to suit everyone. Those who cannot find anything they like can always try gardening in old tin cans.
All together in sun
Lobelia 'Cambridge Blue'
Osteospermum 'Blue Streak'
Pelargonium 'Ville de Dresden'
Nasturtium 'Empress of India'