Depends what you want it to be *for*, really. If the Lords stays as an amending chamber, subordinate to the elected Commons, then the need for it to be directly elected is somewhat less, and it surely becomes more important to ensure that the "amenders" are technically well-versed and apolitical. (Of course, there's a lot of politics in the Lords currently, so this in itself still leaves room for reform.)
But by contrast, any elected body could claim to have more power as a result. For example, suppose the Lords are elected by, say, some form of proportional representation. Then firstly its members are obliged to heed political forces, rather than purely serve as an amending body; and secondly, it could even argue to be more representative of the UK as a whole than the FPTP Commons, and claim more power as a result.
In my ideal picture, I suppose I see the Lords as filled with only what we'd now term "cross-bench" peers: business leaders, technical experts in the relevant fields, scientists, maybe a few with political experience; and with appointees serving strict term limits of, say, no more than 15 or 20 years. In this sense, you get a useful balance: the Commons remains supreme, because ultimately the will of the people in Parliament must win; but the "Lords" serves as a useful quality control, ensuring that the legislation passed by the Lords has the necessary technical input and debate so that it can be effective. But, in particular, you get a balance where it remains clear as to who should win. In a system like the US, for example, where the (elected) Senate is the Lords and the (also elected) Representatives the Commons, their powers are effectively equal in terms of crafting legislation, leading to situations where the two "compete" against each other -- in recent years especially, leading to stagnation where very little of significance is achieved at the Federal level. There are multiple other issues with how things work in the US, but it's definitely one issue that each body can claim electoral legitimacy, even when they aren't aligned the same way, so that there's no way to resolve deadlock by appealing to who ought to be the "senior" in terms of representing the people.
How this applies in the UK in future I don't know, but at the very least I think it's clear that the Commons couldn't claim supremacy for historical reasons if the Lords is redesigned so as to be elected. But the new House of Lords' role would have to be clearly laid-out, and its make-up should reflect that, and I don't think this should necessarily mean direct election.