The return expected on Prize Bonds will be about 0.27% -- that's about one €50 prize per month on €250k. Grossed up, it's the equivalent of 0.43% from a deposit account before DIRT. So it's probably better than you'll get from a deposit account. On the downside, you have to keep prize bonds for an initial period of three months, and there is some paperwork involved (true for a new bank account too). The shorter the period the Prize Bonds are held the greater the chance of "lumpiness" in the return, i.e. the prizes might clump together so that you miss out if the time horizon is only a month or two.
Personally, when it gets down to quibbling between €50/month or €20/month return on €250k, I'd take the path of least resistance, whatever happens to be handier. Non-risk returns are derisory whatever way you look at them.