Surly Straggler or ECR

New to gravel riding --- can't make my mind up on a mtn bike frame or road frame to play on these roads. I have a road bike and a mtn bike already so this would be my all-arounder for fun on back roads and putting some miles on it. I really like Surly \nAny suggestions?

I own both bikes.

The ECR is a great choice for multi-day off road adventures. It's the Willy's Jeep of bikepacking bikes. 

But if you're just looking for an all-around bike to explore gravel/dirt roads as day rides, a little pavement now and then, maybe even some light touring, I'd definitely go with the Straggler. 

Thanks for the input- lol I may have to buy both. Now I need to decide which one to get first. \n 27 1/2 or 29er on ECR?? \nI currently have a specialized epic26- about 15 yrs old. The 29 seems so big

They are nice bikes but I didn't like the fit. Please understand that's not intended to be a criticism of the product. Their Salsa Fargo and Vaya cousins made me feel in control and more comfortable. The Surly models made me feel more old school stretched out.

The black powder coat of Surly bikes is probably a better than the pretty metallic paint my Fargo has.

FYI: This tire thing can apply to many bikes you try. It ended up where I got a near mint Fargo that has faster than stock tires. That trial was lucky in a way because I could tell instantly that it was a better road or commuter bike than was perceived while testing stock bikes. I love having a bike that moves plenty fine in pavement and with way more confidence off of pavement.

If you have a 15 year old MTB with heirloom wheels you should try new MTBs too. We use a modern 29r MTB with semi-fast tires as a great gravel grinder and short distance commuter. That checked off a bunch of items for the past 4 seasons.

I think my delay gratification, spreadsheet and try stuff rule for MTBs should apply here. I tried a bunch of bikes that would all work for gravel and looked at my table that showed reach, stack, angles bottom bracket and wheelbase I know I liked.

Have fun shopping!