In the past few month I have started playing more often Polish Club, as opposed to standard five card major sistems like sayc and 2/1.
Main reason for that was to avoid so many misunderstanding on undiscussed sequences. It did help a lot in this aspect. First of all, there are at least three major styles of playing 2/1, and if you don't take time to discuss what particular version you play you are very likely to get in trouble on simple sequences. Then most players add their particular style and ideas. Truth is there is no standard of 2/1 that has imposed.
Sayc is more simple under this aspect. There is a certain standard. However, my opinion is that sayc is slightly inferior compared with 2/1, and that is the majority view, as most people made the switch towards 2/1.
Polish club is quite different. There is a standard version, that is well described and maintained. It can be freely downloaded from the internet, the WJ standard. From 5 to 5 years, they release an updated version, the latest beeing the WJ2005 standard.
Now stricly comparing the efectiveness of the systems, I will say the Polish club is generally easier to use. Bidding sequences are more clear and effective, despite some bids having multiple meanings. It never happened to misguess the meaning even with opponents interference.
Another aspect where Polish club is superior to 5 card major systems is that it does not neglect the minor suits.
Contrary to what most people think, the Polish Club is a natural system. Looking in a simple way, you exchange the 2 clubs atrificial strong with the 1 club multi meaning bid. In 5 major systems 1 club is not that much of a natural bid anyway, since it is usually minimum 3 cards, or even 2, while the 2 clubs bid played in polish is trully natural. However, the 1 diamond response over 1 club is no longer natural in Polish, still you will be albe to show diamond later.
Generally I would say using the Polish club is easier to use and you are generally better placed in the bidding. However I have to say that I did not play this system long enaugh to explore so many troublesome positions.
The 5 card major systems are more sophisticated and difficult to master. I think you need to find a player about your level that shares your views of the auction to make it more effective than a polish system. It might be better if you have it sorted out with your partner very well.
Whatever system you choose to play, I recommend reading the WJ2000 or Wj2005 polish club standard, as there is a part on Conventions that are used in both systems. You will find good descriptions and explanaitions for most usual conventions and also the slightly difficult ones, like cuebids, splinters, game invitations, and others.