Posted: 28/02/2013 at 13:55
It's nearly always better to buy small, plant well and watch them grow, whatever the shrub or tree. If you're new to gardening this is especially so since you have to get the planting hole and after care right to avoid checking, or even killing, a more mature plant.
Find yourself a good garden centre or nursery somewhere nearby where you can look at and compare several specimens and ask about the kind of care and conditions they need. Acers generally don't like full sun, need shelter from winds and extreme cold and like a neutral to acid soil with good drainage but plenty of moisture.