Well, the way I see it, the Shadow Spirit has some significant problems compared to the Vulcan 750. As long as the engine in your Vulcan is still good, I would keep it. Don't know what your starting problem is, mine starts fine hot or cold.
IMO, the Shadow Spirit is a great looking bike, probably the best looking 750 Shadow Honda has ever made. But, Honda, and all motorcycle manufacturers these days it seems, have a habit of making great LOOKING bikes, while cutting way to many corners to keep their profit margin up. While the Shadow is a solid well made bike, it is lacking some of the really important features that make the Vulcan 750 such a great bike, both for commuting and cross country riding.
First, the Shadow has wire spoke wheels, which mean tube type tires. It also has no centerstand. That means when (that's WHEN, not if) you get a flat tire, you are SOL. There is no way to fix it on the road, whether you are a thousand miles from home, or just down the block. Either way, your stranded. The Shadow is also chain drive, And again, properly maintaining a chain drive without a centerstand is not easy. I used to believe that maintaining a chain drive took a lot more time than a shaft, but with the Vulcan I found out it actually comes out about the same overall, due to the spline lube thing.
I also own a Rebel, an '04 that I bought a few months ago, as something to play with and modify. It has the same issues as the Shadow, but is much smaller and lighter. To lube the chain, I just put a piece of 2x4 under the sidestand, then lift up the right side of the bike and put a block under the swingarm to hold the wheel off the ground. For flat tires, I fabricated an emergency centerstand, which requires removing the right footpeg bracket, placing a piece of 2x4 under the sidestand, bolting the support I made to where the right footpeg bolts to, lifting the bike up, and extending the support to where the bike is off the ground. I have also done this with a number of dual sport bikes. But I cant see being able to lift the Shadow like that. The centerstand, cast wheels, and tubeless tires are the main reasons I originally bought my first Vulcan 750, then I found out a lot of other things I liked about it. and a few things I didn't, mainly the spline thing, and the issues I've had with the cam chain tensioners.
So, after having said all that, IMO, the Shadow is not nearly as practical as the Vulcan. The flat tire thing alone would keep me from owning one. Jerry.
I am a motorcyclist, NOT a biker.
1997 Vulcan 750, purchased about a week ago
2006 Sportster 1200 Low
2013 Royal Enfield Bullet 500, converted to carb
2001 Yamaha XT225, heavily modified
2004 Honda Rebel 250
1979 Vespa P200E
2002 Vulcan 750 parts bike
1994 Yamaha XT225 parts bike