Doses of flax seed oil vary greatly. Taking capsules offers a very convenient method of administration but you become limited in the dose due to the hassle of taking too many capsules. The average dose of flax oil would be somewhere around 4g-10g (4000mg-10,000mg) per day. Most capsules come in 1000mg doses which would require about 4 capsules daily to get the lower end of the therapeutic range. Liquid flax oil can offer as much as 10,000mg per tablespoon. Due to the nice taste of flax oil, taking a liquid is very easy. Capsules offer the convenience of being able to take it on the go or while traveling.
Aside from what is easier for each individual there is no benefit from taking one form vs. another. Certain individuals may require higher doses to achieve the health benefits they desire. In these situations I would recommend the liquid based product because 1 tablespoon would equal about 10 capsules! Taking the liquid is not only much easier in this situation, but also becomes far more economical as well.
The most important thing regarding flax oil is too make sure it is hexane free, which means the oil was extracted without harsh chemicals. In addition, it should be cold pressed to reduce oxidation and if possible, buying organic means the crop the seeds were harvested from was raised without the use of pesticides and herbicides. This makes it better of our environment and for your body.