Overall, the HDS will be a brighter, more capable and intricately engineered light, but I say go with the Jet for the following reasons:
Cost- the U60s are being phased out and there are better things on the horizon, so it's approx $70 for the Jet and $130 for the HDS. Nuff said.
Ease of UI- the Jet is more intuitive (IMHO) and doesn't require as much clicking to get what you want.
Battery type- I prefer using AAs due to their cheaper and more common offline availablity. NiMH rechargables are much cheaper and safer than lithiums
And most importantly to me...SIZE/WEIGHT- the lights are almost the same length, but the Jet is MUCH thinner and lighter, making it more comfortable to pocket (next to a wallet for example) and more likely you will have it with you when you need it.
Overall, the Jet can do most of what the HDS can do under normal circumstances, but it comes in a smaller, lighter package that uses common batteries and costs half the price. It has the same terrific white beam, and an excellent finish.
The only reason I would go with the HDS is if you really need the extra lumens on "high" and already have a stockpile of CR123s or RCR123s. Obviously there are other advantages to the HDS (customizable levels, potentially much lower "low," thermal LED protection, rocksolid regulation, perhaps a more robust build quality/waterproofness), but for my money, the Jet is an excellent compromize EDC that does all I ask for. That said, I am curious to see what HDS will roll out with next, as they do make a superlative product.
Best of luck,
Jon