Both are good units. Garmin tends to be more user friendly, but tends to have proprietary fittings, units etc. Simrad is solid stuff that the pros tend to use. What ever you do, don't go Raymarine. Speaking from experience they are seriously complicated.

 

Didn’t look at the Simrad, just replaced a Hummingbird Helix 9 with a Garmin Echomap 10. It was dash mounted and the Helix was wider than Echo 10. Had to make a cover plate out of starboard to mount it.
I went Garmin due to ease of use and friends have similar units. Had a conversation with guys at Breakwater at the boat show they mentioned that Garmin bought Navionics and the new units include the Navionics maps.

Have not had it out yet - but looking forward to using it.

 

I had both, while the Simrad was more user friendly the 10" Garmin seems so much bigger. If I had to pick one it would be the Garmin.

 

I have always had Garmin and do currently on my boat but I was driving around my friends new Magnum with a simrad (it was huge, definitely not a 9") and will get that unit on my next boat. Super clear and easy to use. Never even used or seen a simrad and had no problem using it. Also, Garmin is getting so proprietary the base map now sucks compared to the base map on my 3 year old unit.

 

What ever you get make sure it works with Navionics!

 

Simrad or a Lowrance 9" screen either would get my vote and Reef Recon looks / displays better on them. Just don't get the newest Simrad NSX as it's not compatible with Reef Recon (if you are fishing Galveston anyway).