Both sclerotherapy and thermocoagulation are effective treatment for treating spider veins and both have good long-term results. Having said that, there are major differences between the two treatments and which one that you should have done is determined by many different factors after discussion with your vein doctor. Some of the main differnces in the treatment are listed below:
1) Sclerotherapy involved injection of a chemical into the veins, therefore also requires a needle be inserted into the veins.
2)There is more bruising with sclerotherapy
3)Thermocoagulation uses heat energy to remove the veins, and the heat is trasmitted through the skin and into the veins by a thermal probe (either laser, radiofrequency, or electrical heat energy is used)
4)Thermocoaulation has a small risk of heat burns on the skin that can sometime lead to scarring of the skin
5)Sclerotherapy can usually treat a larger number of veins in a shorter prior of time since the medicication moves to many of the abormal spider veins with a single injection. Surface thermocoagulation involves a "spot" technique that treats a small focal area at each "zap" and therefore often takes the doctor a longer period of time to treat a small area. This may translate into sclerotherapy being more inexpensive for the patient since the treatments don't take as long.
6)Sclerotherapy has a small risk of drug reactions or drug allergic reactions, whereas since thermocoagulation does not involve medications, this risk does not exist for thermocoagulation
7)Thermocoagulation is only effective for very small spider vein
8)Sclerotherapy can be used for many different vein sizes, even larger varicose veins as well as small spider veins
9)Sclerotherapy is rarely used on the face or nose, whereas thermocoagulation is commonly used on the face and nose
Since there are so many individual factors that play into whether sclerotherapy or thermocoagulation / laser is the better treatment for you, it is best that you meet one-on-one with a vein specialist to discuss your options and determine which one he recommends for your specific situation.
I hope that you found this information helpful.