I'm torn here.
For starters, I've always hated the SHD because of its stumped jump ("hop") capability, because it couldn't keep up with its fellows. 5/8/5 is just a natural movement profile, especially on the Wolverine, Griffin, Dervish - the typical buddies of a Shadow Hawk - and also on the Quickdraw and the Dervish's FedSuns sidekick, the Valkyrie.
What are jump jets good for? Personally, I don't value them much in a fight (as in, a round in which I fire weapons/have LOS to enemy units) because jumping will ruin your targeting and frequently generates debilitating amounts of heat. So I use jumping for basically two things: positioning, and as an exit strategy to get a 'Mech out of a bad situation.
In the latter case, you absolutely want to have as many jump jets as possible. 3, not to mention the UrbanMech's 2, just aren't enough to get out of the danger zone in most cases. 4 is the minimum amount to be useful for jumping a 'Mech to safety, and you really need 5 to be on the safe side in my book.
In the former case, positioning, even 3 jump jets can make all the difference in the world. In my last pickup game of BattleTech I fielded a lance of LCT-1V Locusts against an Enforcer and a Spider - and although I won I was reminded again just how much speed isn't armor even in a 3025 tech setting. There was lots of hills, woods and rivers on the maps (the endgame played out on a "River Valley" map iirc) and jump jets made all the difference in maneuvering there. In particular, crossing a stream without jump jets makes 'Mechs sitting ducks, as not only my Locusts but also Aidan Pryde can attest to. Even a jump capacity of only 3 would have spared me a lot of headaches and lost armor. But I'd still get outmaneuvered by the faster jumpers.
Ultimately, my conclusion is that 3 jump jets are insufficient and a 4th adn 5th jump jet is worth more than their equivalent in armor.