Hi.
If you are planning on getting coated titanium valves, I suggest you look into a DLC coating. It is superior to TiN and any other ceramic coating in every which way except color, in which it's a toss up because DLC is black and TiN is..gold. But it's your valves so nobody is going to see anything.
DLC is also superior to any other coating except cost and consistency of application. Find a reputable place that will apply it correctly, because it is usually "spray-sputtered" using a CVD/PVD process that leaves lots of potential for surface ireegularities and film thickness lapses. It simply means that extra time and carefulness must be taken into account which usually drives up cost.
DLC is an amorphous solid, giving it superior strength in most areas of mechanical stress when compared to regular crystalline solids. For example, DLC will "bend" (up to a limit of course) with the substrate that it's adhered too. TiN for example is a plating, so it has a greater chance of flaking off and cracking. Don't know why Ohlins still uses TiN on their fork tubes other than that it's kind of their namesake. In my opinion, DLC is the best coating out there. TiN is also easier applied, giving it consistency that takes more time when applying DLC. But whatever, they're a good company so I'll refrain from saying anything else haha.
It also greatly reduces friction. Great for valves, camshafts, fork tubes, whatever.
I don't think you will notice too much between the two. If you get any coating, it will extend valve life greatly. Leaded fuel should not be a problem; deposits shouldn't adhere to the valves as easily because of the reduced friction.
You can also look into coated steel valves. Probably cheaper, just not as light as titanium valves.