These two companies are quite comparable in many respects, so it may come down to rates and the coverage options you prefer. Safeco has more extended coverage programs and a stronger safe driving program. It also has the Diminishing Deductible option.
Travelers tends to get stronger marks on the way they handle claims. It also has a mobile app, and Safeco does not. They have a slightly stronger customer service rating according to the Better Business Bureau, but both are strong in this regard. They also have the exact same customer service rating from JD Power and Associates.
Every insurance company underwrites their policies differently, so get a quote from both of them. Make sure it's an apples-to-apples comparison, then think about adding some of those optional coverages to get a fair assessments of the rates you'll receive.
Two different people might get totally different rates depending on the discounts qualified for vs. the discounts offered by each company.
Safeco vs Travelers: Speak with your insurance agent if you aren't sure. Agents can often help you spot the benefits of choosing one policy or another when you might otherwise miss them.