The benefit of the larger bed is that your child can have a friend to sleep-over and simply share the bed. The other option is a trundle-bed or pull-out bed which is stored below the bed. It all depends on the size of room you have to work with.
Beds come in many shapes and forms. When you find one you like, take a closer look. A child's bed will be a sofa, a trampoline, a den and, occasionally a place to sleep, it will take more abuse than any other bed in your house so check out the materials, and double check the hardware that holds it all together. Get onto the bed and sway left-to-right and up-and-down; give it a bit of a bounce; now pull back the mattress and keep an eye on the corner connectors while you push and pull on the joint. If there is movement when the bed is new, you can bet that it won't get any tighter with age; there should be no unacceptable movement, no creaking or cracking. The best bed connectors I have found are the Australian Maxi-Lock bed connectors which key together and tighten up with a threaded bolt. Most UK beds still use the traditional ‘hockey-stick' type connector which are okay if they are fitted correctly. Regardless of the type of fitting, check it for strength and slackness.
There are two main types of foundations:
The Box Spring bed utilises a sturdy upholstered wooden frame containing springs or some other form of torsion. The box-spring serves three main purposes: To help raise the mattress's height; to help absorb shock and reduce wear to the mattress; and to help create a perfectly flat and firm structure for the mattress to lay upon.
Wood Slats are common, and these usually consist of at least a dozen solid wood planks strung together and fixed to the bed-rails. The slats should have soft edges, not machined to a sharp corner edge, or they will damage the mattress. They should be of good knot-free timber and preferably no more than 50mm apart. The main benefit of using a slatted bed is that you have much better access to below the bed for storage, retrieval and cleaning. And it allows the space for the pull-out trundle-bed.
Theme beds, such as car-beds, train-beds, digger-beds, fairy-tale designs, etc. Pay particular attention to these beds. These bed designs cost more to manufacture, so it is not unusual to discover that the manufacturer has attempted to save a little money and compromise the quality which will effect stability, and serviceable lifetime of the bed.
Buying a bed online is made really easy nowadays, but there is nothing to beat going to a shop and handling, kicking, lying on the bed to check it over before you part with your money. If you buy online be sure that you have the option of a full refund for ANY reason; and that refund should include pick-up from your home. Most retailers will demand that the goods are returned in original condition and that the original packaging is used, so if in doubt, hang on to the packaging when you first receive the goods.