Spain's unemployment rate, for instance, is at about 22.5 percent – the second highest in the 19-country euro area after Greece.
Portugal, meanwhile, has a debt-to-gross domestic product (GDP) ratio of about 130 percent – one of the highest in the euro zone.
"It's better to invest in something that is weak and improving (like Spain) than something that is strong and stable. So, I'd rather invest in that market," Hans Stoter, chief investment officer at NN Investment Partners, told CNBC on Thursday.
"Also, from a government bond market perspective, the European Central Bank possibly stepping up into the next gear of QE (quantitative easing) would be positive for peripheral spreads."
A poll released this week suggested for the first time that the center-right coalition in Portugal could return to power in an election scheduled for October 4, Reuters reported. All prior polls had shown a tight gap between the country's two main parties.