In Depth: Bridges vs Tunnels

Bridges

           VS

                                                                                         Tunnels

Bridge Pros:

• The view can be amazing depending upon location
• There's always a clear shot of where you're headed 
• Not claustrophobic
• The architecture is almost always worth a look
• Many bridges are tourist sites all in themselves, giving you bragging rights

Bridge Cons:

• It's a straight drop
• Acrophobic
• I've seen "The Mothman Prophecies" and that would suck
• Many bridges are tourist sites all in themselves, meaning traffic
• By the last estimates, roughly a quarter of the bridges in the US need repair
• Trolls are notorious for living underneath and eating goats that attempt to cross

Tunnel Pros:

• It's like travelling through another realm
• It can be quicker, cutting the distance
• Can be more durable than bridges
• Supposed to be safer
• Not acrophobic

Tunnels Cons:

• Ugly, nothing to see
• Claustrophobic 
• I've seen "Daylight" and that would suck
• Getting stuck in traffic underneath a large body of water, or under a mountain... not fun
• Dwarfs are notorious for living in underground tunnels and robbing people who pass through

After reviewing all the pros and cons you can see that there's no clear winner. I would suggest as the best alternative to plan for extra time and just go around said object.