Question
Homejoy and Exec are the perfect examples of companies that have gone very deep into their one offering, house cleaning. While other companies like Thumbtack and MyTime have gone very wide to gain more marketshare, faster. MyTime and Thumbtack offer every service under the sun. They are creating demand and then finding supply as they go. I am not sure if one strategy is better than the other when it comes to creating a marketplace for services website.
Answer
Depends on your business model.
If you search you'll find examples of businesses that have had success with both of those models (and if you are starting with a "preference" for one or the other - beware of confirmation bias).
Your question also states that you are after "more market share, faster." Another caution is to beware of vanity numbers and lack of specificity.
If you've mapped out a good business model you'll know your numbers (projected margins, cost of acquisition, break-even points) - and instead of using vague qualitative words like "more" and "faster" you will have targets that you can track and key metrics to measure.
If you are interested in how to quickly map out a business model perhaps we should talk. In any case - Best of Luck!