Each time you spit the antenna up with a trap or coil you lose some of its radiating efficiency. That is not to say that it won't radiate effectively, it will just be less than optimal for any one band. Kinda think of it like this, in a sense you are tricking the antenna into thinking it is longer than it actually is for some bands, and not for others. Like silly putty you are asking it to take different shapes on.
In our discussion over the CB antennas, the 102" whip will far out-do the firestik (or similar) antenna, simply because you are putting more metal into the air.
The home brew 5/8λ 2M antenna will out perform a dual band antenna for 2M and 70CM. The difference might be unoticable for your purpose. Same thing goes for single band vs multi band yagis. A single band yagi will have maximized forward power and gain for the band for which it was designed. A tri-bander will have forward power and gain maximized to work for all three bands, not just one.
So to put it this way, if you use all four bands regularly, it will be more beneficial to you to get the 4 band antenna. If you think you will play mostly on 2M and for fun do 70 CM once in a while, stay with a dual bander. If you don't think anything other than 2M will be of use to you, get a mono-bander. Remember, too, that the quad band radios are usually for 10M FM, 6M FM, 2M FM and 70CM FM. 6M is said to be the magic band right now, with awesome opnings frequently allowing 1000 mile plus transmissions, 10M FM is not that busy.
Do what you like and what interests you. Go for it all. Play with it
, its what makes the hobby fun!