Hotel - city center vs Sloterdijk Station?

We prefer to take it easy after dinner and we will most likely just come back to the hotel after dinner and rest,

Then IMHO, you should stay in the center of the city. After we had dinner one of the many restaurants in Central Amsterdam, we walked back to our hotel located either in the Jordaan district or near Amsterdam Central. To get to Sloterdijk, you would have to walk from your restaurant to the train station and then take the train to Sloterdijk.
If you stay near Sloterdijk station, you will have to take the train to/from Sloterdik station into central Amsterdam every day.
All the landmarks and activities are in central Amsterdam, and if you google view the area around Sloterdijk station, is this what you really want to see and be surrounded by?
For Keukenhof, if you buy the combo-ticket (admission and transportation) you will have to train into central Amsterdam to catch a bus or train to Schipol airport to catch a bus from there to Keukenhof. Sloterdijk station is WEST of Amsterdam Central Station and Keukenhoff is South and West of Schipol airport. Though it may be possible to take the train from Sloterdijk station West and get off somewhere near Lisse and taxi from there.
What hotel are you thinking about near Sloterdijk station? They'll typically be modern chain hotels. SoHow about looking at the Doubletree near the Amsterdam Centraal Station, if that's the kind of hotel you want?
I take it you are looking at Sloterdijk because it's cheaper? I think that's Penny-wise but time-foolish.

I stayed in Amsterdam for 5 nights last October, and struggled with this same choice. I went with Sloterdijk (Holiday Inn Express) for the train connections, being able to skip Central when arriving from Brussels and departing to the airport, plus day trips to Delft and others, but an easy hop into Amsterdam as well. I had doubts about this choice (pretty bland compared with quaint b&b on a canal, right?) but these days I prefer manned front desks and elevators in most places.

Well, it worked great for me. Decent restaurant next door, and a minimart as well for snacks. Nice and quiet. There is a tram line that runs directly to the city museum district, tho it wasn't running when I was there.

There's nothing wrong with staying by Sloterdijk, and I think it has its highlights (Westerpark was interesting) and has the cost benefit. However, especially when balancing time vs cost savings, I generally go more towards optimizing my time over only relatively small savings of money.

When you're closer to the "action" - say in Leidseplein or Jordaan - you can see more and experience more OR see the same but with a lot less effort. Most of the "landmarks" folks are seeing in a short stay in Amsterdam will be in the more central parts of the city - museums, parks, restaurants, shopping, canal boat tours, and walking tours will all mostly be a short walk (or better, quick bike ride) away from hotels in those closer in neighborhoods. To me, prioritizing the time you have in town is much more important than some cost savings.

I've stayed at Sloterdijk before. Amsterdam hotels are expensive, and if staying at Sloterdijk helps you afford your trip better, I don't think there's any problem. It's awfully close, and there are trains there constantly.

Is it as charming as staying somewhere close in? No. Do we all have unlimited lodging budgets? Also no. Sometimes we have to make trade offs. Only you can know how much money you would save/spend, and how much that is worth to you.

I've not stayed in Sloterdijk and not really been to the area, but I've changed train at the station once as well as passed through it. It hasn't given the impression of being a nice and charming area worth staying in, but the station is a bit of local hub with good connections, and there are several hotels there that are probably a bit cheaper than the hotels in central Amsterdam. So not a terrible idea, especially if you're only planning to spend two of the five days in Amsterdam itself.