2 small trees for 6 x 12m garden. Both similar or different?

[erebus]

I have a smallish garden with a hard-standing that will become a patio in the far left corner. I want to place 2 trees, one in front of the standing, one to the right (as you look at it from the house) so you'll look through the 2-3m gap formed by these trees onto the patio.

Now, should I get two similar appearance trees (if not identical) or go for 2 quite different ones?

Naturally both must have an upright habit and moderate overall height.

We have been thinking:
Silver birch, white trunk variety
Silver birch, red trunk
Mountain ash
..for examples

Thanks for any input

I'd go for different trees, so that their periods of interest aren't exactly the same.

We have a silver birch, a yellow berried sorbus (TBH I wish now we'd got normal red mountain ash), and have recently got a whitebeam, which is also in the sorbus family but looks quite different, larger silvery green leaves - as the guy in the nursery who advised us said, its a pretty tree.

If I was getting two trees at the same time I'd consider fruit trees too - many aren't self-fertile so rarely a good idea to get just one.

Mountain ash is rowan. Its a small tree versus an oak or beech.
Silver birch is probably about 50% bigger than rowan, but some of the red (or lovely chestnut) trunked birches are usually quite a bit smaller.

I'm rubbish at imagining what 6x12m looks like so don't know if they are the right scale but presumably the OP has/will look at mature trees of the types mentioned.

Cherry can be nice but they tend to be a bit wide for their height.

A lot of people with kids won't want laburnum because of the poisonous seeds - not that I've ever heard of a kid eating them.

One other thing to take into consideration - ask advice at the nursery - is what the roots are like. Some trees really shouldn't be planted near houses, and so presumably could affect the patio. We were told the whitebeam had non-spreading roots so was good.

You can get varieties of rowan which won't grow so tall - we have one in our garden. I can't remember quite how big it's meant to end up, but much less than the ordinary native ones.

How about an amelanchier? They stay small, have lovely blossom and berries and fantastic autumn colour.

I'd get two trees in completely different colours, and plant the taller one at the back. So if you're having a silver birch, then maybe get a red japanese maple, or a yellowy ginkgo biloba (not sure how big they get eventually but very pretty), and I'd also put some contrasting grasses underneath in blue/green, black, yellow/green etc, preferably with interesting seedheads.

I've got 5 trees along the back of my small garden for privacy and they are all different. We also have a Sorbus aria - very pretty and upright and I also have several cherries and a Robinia which is very attractive. All are suitable trees for a small garden and according to the garden centre have roots that are not too invasive.

Thanks for the input everyone. Any more always welcome too, of course!