For 250K in economy, I would prefer UA Mileage Plus. You could earn 12 SWU (systemwide upgrades) per year once you qualified (i.e. the first year, you would earn only 6 I think). Each of these can be used to upgrade an entire direction of travel on UA, not just a single flight. You would likely earn a bunch of Region 1 upgrades (which depend on how much you fly UA only). Those can be used anywhere UA flies in North America and nearby areas, which makes for some long flights upgraded.

If you ever fly Y or B fares on UA (or LH transatlantic) you earn 50% more EQMs (same redeemable miles). If you flew a substantial amount on Y and B, you would earn even more SWUs. Note that all *A miles count toward earning SWUs (only UA miles count toward Region 1 upgrades).

On that note, if your economy fares are high enough, you might even be invited to United Global services, with more perks. Living outide the USA makes this easier as you are competing primarily in your own market. If you always buy super-cheap economy fares you probably won't be invited.

UA also is increasingly offering upgrades for cash for $350-550 per segment when space is available and at your pace of travel you might want to take advantage. You can also request confirmed upgrades for 30K miles per one-way on 15K miles for Y and B fares. If you have the ability to purchase some Y and B fares, you can upgrade those with miles and save your SWUs for the lower coach fares. There are one or two coach fares that don't qualify for SWU usage, but most do.

Charles