Depending on where you plan to meet, a client dinner could actually be tricky as the various neighborhoods in San Francisco offer quite different crowds/atmospheres. If you are near The Embarcadero, Slanted Door is a great spot. It has a HUGE menu of exotic but strong Asian dishes, and it's very classy ambiance. I highly recommend their chicken in a clay pot dish- it's something I'll never forget eating.
Closer to Union Square, but VERY MUCH off the beaten path is Le Colonial SF. It's another restaurant with Asian influences (order at least two plates of the glazed brussell sprouts to start...trust me!). I'd recommend this place primarily because of its location; its tucked into an alleyway that you wouldn't stumble upon unless you knew the restaurant was there. The interior is quite intricate but would be great for a professional environment. 

Another great one would be Aziza. It's Moroccan cuisine, and great quality service- they make a point of not rushing you out of the restaurant. 

Khan Toke Thai House would be a great option if you're priority is to give your client a seriously impressive meal that's not just about food, but also an experience. The highly authentic restaurant has its guests dine seated cross-legged on the floor, as is the standard for certain Thai dining traditions. There are separate little enclaves of booths that you will eat at, so you can have ample amounts of privacy while still taking in the ornate environment. Even if you don't decide to go here with your client, please do add this to your list of must-dos anyways! 

Unfortunately I have yet to try Twenty Five Lusk. I have heard great things though!
Good luck with your dinner!

Twenty Five Lusk is pretty great! It has delicious food, a great ambiance for pre-dinner cocktails crafted by their mixologists, and isn't too pretentious. A few other options are Foreign Cinema that has a great open patio where they project old movies on a huge brick wall (no sound). SPQR is phenomenal italian fare with an extensive wine list. Frances is a local treat in the Castro with farm to table delicacies (go for the duck liver mousse!) but a bit quiet. Nopa is a blast, is a huge space with two floors with an open balcony that over looks the whole restaurant, has a great bar, and is always packed (make reservations!). Park Tavern in North Beach is phenomenal "new American" that has a huge dark wood bar and checkered tile which ironically channels a french bistro feel. A more casual but incredibly fun, lively spot is Delarosa in the Marina - they make a mean salty dog and have some of the best pizza in the city. Two other Marina hotspots are Terzo - great fire pits, fun ambiance, and have the most delicious steak with chimichurri sauce, and A16- impeccable pastas and an extensive wine list. 

I've never been to Twenty Five Lusk but if your goal is to impress clients my recs are:

State Bird Provisions
Foreign Cinema

Seven Hills

And of course the no brainers:
Michael Mina
Salt House
Gary Danko

Also can vouch for Slanted Door. Good good stuff.

if you're in the mission, I like Locanda. 

Italian with a good, busy vibe. Last time there we had the bourbon tasting flight, which was nice, and it will get your clients loose. 

Twenty Five Lusk is great for cocktails, but I would skip it for dinner. It's also quite the scene.  At those prices there are much better places in the city. Also, last time I ate there, the bar/restaurant was filled with escorts and their clients (which may or may not be something you are looking for)... 

I love Roy's Hawaiian Fusion, Dosa at Filmore and Osha Thai. You can also go to Slanted Door or Greens Restaurant at Fort mason.

Kokkari Estiatorio- Stellar food and great decor; a little exotic, but not too much.  Boulevard has an old San Francisco feel and consistently excellent food for every taste.