Shadow phantom or street 750?

I'm looking to upgrade from a Honda rebel which one do you think is a better overall bike and is safest for a 17 year old thanks guys

The Shadow is more likely to be reliable as it's an older platform and has been made in one form or another for a couple of decades and it's a Honda which you are familiar with.

The Street 750 is a brand new motorcycle by Harley - its first domestic water cooled attempt and a new displacement category for them. So far it seems to be met with decent reviews. Time will tell if it's a good first effort for them for an entry level bike that's not a sportster.

Shadow.
Hands down.
The Honda has a rear drum brake which most dislike, but I love.
Shaft drive, low maintenance.
Low compression, may be able to use mid or low grade gas to get home.

The HD has disc rear (dislike my current HD disc).
Belt drive. Most like, but I lost 2 before converting to chain.
High compression, requires 91 octane or better.

I have had a number of Hondas, and the only problems were the ones they had when I bought them.
I looked at the Street during Bike Week. Had it to highway speed on the "rolling stand". Didn't like the sound or feel. Fit and finish… Poor.
Exposed wires, connectors in the breeze.
I've seen cheap imports that looked better.

From previous questions, I get the impression this would be your first bike.
If you insist on buying new, clear choice is the Honda.
Of course, I'd recommend buying an older, used one.

Compare: http://www.powersportsnetwork.com/enthusiasts/new_vehicle_compare.asp?vehicle1=414047&year2=2015&mfg2=1&vehicle2=433043&go=Go

I prefer the Harley Davidson.
Same MRSP.
60 pounds lighter
Cast aluminum wheels -- tubeless, no need of rib strips and tubes. Safer.
Belt -- good for 100,000 miles before replacement. No need for getting replacement cogs/chains not mentioning the grease.
Far better performance. (oh yeah, gotta use premium gas. 20 cents more per gallon, 5% more money for 10% more performance.)

Ride each one and then choose.