Heavy Bag- Banana?

I know this has been posted before:

I am thinking about getting a bag for punching and kicking (developing shins). Should I get a standard boxing heavy bag, or a specific MT banana bag.

Also, if a banana bag is suggested, which is more practical- 4ft or 6ft?

I am leaning on Fairtex's filled 4ft at the moment:


get a 6ft bag, if you can't afford it SAVE up until you can...

Better get the 6ft unfilled for under $140 and fill it yourself.

Unfilled 6 footer for $90