I think if you are not going to be jumping huge jumps and you don't really have an issue with your saddle slipping, then a 3 point style breastplate should be fine for you.
I own a couple of 3 point breastplates and a 5 point breastplate. I like them both.
The 5 point breastplate has been very popular in eventing and is starting to gain popularity in show jumping as well now. I can see that using one in eventing is a good idea especially for higher levels whether your saddle slips or not just as a safety precaution. For show jumping I would say that if the jumps are big and /or your horse is having saddle slipping back problems then I would say it would be a good idea then as well, but if you aren't jumping really big jumps and you don't have any issues with your saddle slipping then the 3 point breastplate should work out fine for you.
To make it even easier to fit you can add snaps on the the breastplate so that you can just snap the straps to the D rings on the saddle and if your girth has a D ring in the centre you can snap it on there as well, quicker and easier to fit then. The 5 point is trickier to fit and adjust just right and takes longer to tack up, so I wouldn't recommend it unless you actually need that style.