There are several types of marine sanitation hose. The most basic and cheapest is the white vinyl hose as sold by Shields as their type "Series 148" @ about $5.00/ft for 1-1/2" ID hose. This hose comes in various ID sizes from 3/4" to 3" and is basically the same as the hose you mention for your spa. It is really a general purpose hose. Sealands hose is basically the same but it is supposedly formulated with a compound to resist odors. This is equivalent to Shields Series 144 super PVC sanitation hose. It comes in two sizes, 1" and 1-1/2" and goes for about $6.50/ft for the 1-1/2" ID. Shields also offers a Series 101, black, multiply rubber hose with a green stripe,this hose is commonly refered to as Shields green stripe sanitation hose. This hose has been around for a long time. It is very flexible compared to the white vinyl and is highly odor resistant. It comes only in 1-1/2" ID and goes for around $ 9.50/ft. Top of the line and relatively new is the Shields Poly X sanitation hose. it is the most flexible, and supposedly very resistant to odor, combining rubber, fabric plys and polyurethane. It has a white polyurethane outer coating and comes in 1" and 1-1/2" ID. It is very expensive, a 12-1/2 foot standard length of it goes for around (hang on to your wallet) $250.00, about $20.00/ft
I have used all types except for the new PolyX, and have found little difference between the odor safe hose and the regular hose. In my experience, I still find the SHields green stripe the best, not only in terms of odor resistance, but also in handling (bending radius, getting onto fittings). Perhaps the Poly X is better , but at that price, I have not decided to even try it.
In my experience, keeping an odor free head has alot to do with a proper installation, and maintenence, emptying the holding tank promptly, and flushing out the tank and hoses periodically, especially before any lay-up. Some people even use fresh water for flushing, but IMHO, unless you are tied to a dock with a water hook-up it is a waste of fresh water. A well ventalated head also helps.