I was looking for everyone's opinion on what they think which hotel reward program suits me most.
I looked already on the internet about reviews about different programs but the reviews where mostly based on US residents.

At the moment I am on vacation in the US and I noticed there are a lot of properties of Hilton and Marriott brands even in the smallest towns.
But in Europe they have less properties. Madrid has only one Hilton property.

I spend around 50-60 nights a year in a hotel. Most of the time for leisure. My travel area is mostly Europe, US, Australia and occasionally Asia. I liked my stays at hotels from the SPG program. But I am not sure this is the right program for me.

I have some factors that I consider important:

- Quality hotels in the program
- Upgrades

Any advice would be appreciated.

Many people invest loyalty in two programs; for reasons you have already pointed out.

I suggest looking into Club Carlson (Radisson Blu, etc.). Great coverage in Europe/Asia/Australia, easy to earn points and higher status. Although they don't have really high-end properties, many European and Asian locations can (and do) rival some Conrad/Hilton locations. Hilton (HHonors) is good for US stays. ^

You will get as many different opinions as you get responses.

Choice Priority is great for Europe (Clarion, Comfort Inns, etc.), and can be had for only 8-10K points. Although whether it suites you or not would depend on your definition of "quality".

Most of the time I stay at 4* hotels. I want to join a reward program with many 4* properties and a few high-end.

Starwood.

Great properties at good prices in terms of awards. Cash + Points redemptions often closes the deal on your question.

With Starwood, the upgrades flow to the Platinums and above, so you'd need to commit 50+ of those nights to SPG. (You could reach Platinum in 25 stays, but I assume a mostly-leisure traveler would tend to average 2 or more nights per hotel.) I don't know how many true 4-stars exist in the SPG system, but I know there are some.

Starwood is a very rewarding program, but you do need to get to at least the base Platinum level to start getting good upgrades.

If your travels take you to too many places that don't have a Starwood, you might instead consider HHonors. They have a variety of fast-track type options to Gold, which gets you *some* benefits. Gold tends to be treated fairly well outside the U.S.

Having a backup with a huge volume of lower-end hotels can be helpful. I've used Priority Club points at a value of a little under a penny apiece in rural areas where no other brand had properties. Carlson seems to have good utility in Europe. Don't know much about Choice...

Then I stand corrected.

I join the SPG program as main reward program based on the replies (Thanks for that) and my own experience I had with some properties of the SPG program.
As secondary program I'm not sure which one suits for me. I think I will try out HHonors and Club Carlson.

As Dutch citizen I cannot apply for a SPG, HHonors or any other hotel chain credit card.
I can apply for a standard American Express card and exchange the membership rewards into hotel points. Is it worth it?

Amex MR is an old standby, some people here still use it as it tends to be a fairly common corporate-issued card for expenses. Whether or not you should get it as an individual is more a function of the overall Dutch credit card market. What other rewards options are out there for you?

HHonors has some non-credit-card Fast Track possibilities for Gold status. All of the hotel statuses have been watered down in recent years but HH Gold still had a few modest benefits, especially outside the U.S.

As msscout commented, Choice is great for Europe. Used points last year at Comfort Inns in Milan and Venice. Also stayed in Tokyo at a Comfort Inn two years ago using points and it was a GREAT deal. If you are looking for 3.5 stars or above then Choice is not for you. They tend to be 2.5 to 3. But if you can live with basically 3 stars, Choice is hard to beat.

If you are staying in major cities in the USA, then Hyatt is good -- many excellent 4* properties. Hyatt has little presence in smaller cities / towns, though -- Hilton HHonors is best for that. The Choice properties seem to me to be more attractive in Europe than the US.

Actually there is no other reward option for me... Credit card is not a very common payment method in The Netherlands.

I took a look at the Fast Track possibility of HHonors, 4 stays within 90 days of enrollment seem like a good idea. Thanks for the advice.