As another flyer who holds both 1K and SEN, I would have to agree that, for the most part, 1K has more benefits. Already mentioned is the comparison between 6 SWUs and 2 e-upgrades (you need two of the e-upgrades to upgrade intercontinental, so the 2 e-upgrades are equivalent to one SWU or 2 CR1s); also, the 1K dedicated telephone lines seem a bit more convenient and helpful than the SEN ones, but that may just be my experience rather than a general rule.

On the SEN side, it has also been mentioned that SEN gets you lounge access in the United States where 1K does not, and that SEN seem to have a wider inventory of award tickets (sometimes at lower cost in miles, but often with higher surcharges).

Two other advantages to SEN: First, for a flyer with his home address in the US, making SEN usually requires fewer BIS miles than does 1K due to the 25% "Executive Bonus" miles counting as EQMs for SEN (on the other hand, M+ sometimes has DEQM offers, while M&M does not). On the down side, though, the Executive Bonus for SEN flights is only 25% (RDMs) as contrasted with the bonus for 1K of 100% RDMs.

The second advantage is that one need only fly the 100K EQMs every other year to maintain SEN status as contrasted to 1K's annual requalification requirement. Along that line, both programs offer "lifetime" status, but M&M's seems much easier for the flyer to attain.

The main reason I strive to maintain SEN status on Lufthansa is that I do fly a lot of European flights, and in my experience LH (along with its partners such as Swiss and Austrian) treats its elites with much more consideration in cases where things go wrong than they would a 1K. That may be just my particular experience, but here are two examples:

When Sabena went TU without warning in (I think it was) 2002, I was in Brussels scheduled to fly out on Sabena that afternoon. When I got to the airport, it was total chaos; all of the passengers who had been planning to fly Sabena had to find alternative transportation or cancel their trips. Some, like me, had flown in on Sabena and were stranded away from their home station. As the stoppage was unexpected, the other carriers had not plussed up capacity, so seats were really hard to find. I went to LH and asked about buying a seat; they asked if I had any status. I showed them my 1K card, and they said they didn't think there were going to be any seats available, but I was welcome to wait. The lady then said, "Isn't that a Frequent Traveler (silver on M&M) card in your wallet?" I replied that it was, and she looked at it, then issued me a ticket on the spot.

A few years back I and two colleagues were trying to fly out of Ankara. For whatever reason, our reservations were not recognized when we got to the ticket counter to check in, and all of us were told we could not board. I requested to speak with the manager, and he came out to the counter saying, "I'm really sorry, but we simply don't have any seats available." At that moment, he saw my SEN card lying on the ticket counter, and asked, "Are you a Senator?" I replied that I was, he looked at the card, and then said, "We'll find you a seat." I thanked him, and asked about my two colleagues. He replied, "If they're with the Senator, we'll find them seats as well." And he did. (My two colleagues were Gold with United.)

I guess my bottom line assessment is that I agree with Jalinth -- it depends on your flying patterns which is better for you. For me, it's better to have the status in both programs.