It really depends upon what you want to play and how.
An arranger will give you a one man band setup without additional equipment.
A digital piano is better if you want to learn to play piano, these have different key actions to the arrangers and hence they are more suited to piano based playing.
@£300 there are two prime arranger options a Yamaha PSR E463 and the Korg EK50. Both have 61 synth type keys and both should last many years if cared for correctly.
The way it is with arranger keyboards is that there are a lot of the beginner boards up to c£300 then quite a gap until you get to the Korg Pa700 and Yamaha PSR SX700 which are about £1000 and these cater for all abilities, even beginners.
In between there are the old Korg 300 & 600 models and a Yamaha SX600 which is a cut down version of their SX 700. There are also the digital pianos with arranger features as per those you may have seen suggested in other threads. Korg EX20, Yamaha DGX670 and Casio PC S3100 are the models, each have their plus and minus points but the DGX 670 probably should be at the top of anyones wish list in this market segment.
Caring for a keyboard, keep in a constant environment as dust free as possible, out of direct sunlight, play it only with freshly washed and dried hands, keep young children off the keyboard, the most important is to keep it covered when not being played by a keyboard cover that is specifically made for this use.
Keyboard covers are snug fit and the material used has a very high thread count resulting in a close weave or knit and is anti static in nature.
Additionally a good quality power conditioner/surge filter should be connected to the mains and your keyboard connected to this. Typically the extension leads you can buy from PC World. I have used Belkin products for many years, not just at home but at work where my role was often in charge of the whole electrical system and all the connected equipment.
