Very, very difficult decision. And it all depends on the assumptions you make.
1) How much is the ETV? I can't imagine that it's that much if you worked there for only 7 years. If it is a large amount, you need to think carefully and maybe get independent actuarial advice. On the other hand, if it's only a small part of your portfolio, it's less important to get right.
2) Are you married? A DB scheme which pays 50% to the spouse is more valuable to a married person than to a single person.
3) Do you have any health issues? On the one hand, the DC would stay in your estate. On the other, your spouse would get half you pension.
4) Do you have to make the decision now? Or can you defer it?
If you put it into a retirement bond, you will presumably invest it 100% in equities. The world is in a very strange place at the moment and having a well funded defined benefit scheme gives a lot of comfort.
5) How does it fit in with the rest of your wealth?
If most of it is in property (your home) and shares (your DC scheme) a DB scheme seems to be a good diversification.
If the other DB scheme, of which you are a member, is the major part of your wealth, then maybe a DC/Retirement Bond is good diversification.