I assume you are talking about the pros and cons for the US, not for the Philippines...
The major pros had to do with economic and military power. By taking the Philippines, the US had access to its resources -- things like sugar, pineapple, and rubber. Also, having more of an empire made the US look like a world power. Finally, it was thought that the Philippines could be a military outpost from which the US could project power in Asia.
The immediate cons had to do with the loss of life and the monetary cost of the annexation. Many Americans died fighting the Filipinos and much money was spent. Much later, it turned out that holding the Philippines was a military liability. At the start of WWII, the US did not have enough military equipment or personnel to defend the Philippines and so the fell to Japan. The US later felt it had to retake the Philippines, again at the cost of much blood and money.
The United States wanted to become a world power around 1900. After the Spanish-American War, we gained possession of some of Spain’s colonies. These included Puerto Rico, Guam, and the Philippines. There was some debate about controlling the Philippines.
There were advantages to controlling the Philippines. We needed military bases around the world if we wanted to be a world power. We had few possessions in the western Pacific, so controlling the Philippines would help our military. We needed bases where our ships could resupply and refuel. This would allow our military to protect our world trade and to be used as a military base in case of war.
We also could trade with the Philippines. We were looking to expand our trade, and controlling the Philippines would allow us to do this. We wanted markets where we could sell our products, and we wanted to get resources cheaply from any colony we controlled.
Disadvantages to controlling the Philippines were seen very quickly. The people of the Philippines wanted to be independent. Thus, we had to fight them for several years. This proved to be costly in terms of life and dollars. Even without a war, the cost of running a colony was significant. There were people who felt we shouldn’t undertake this expense. Other people felt it was wrong for us to control a group of people that wanted to be independent. They felt it went against the ideals of our revolution.
There were positive and negative reasons for annexing the Philippines.
Since the pros and cons for the US have already been addressed, I take this opportunity to address the pros and cons for Philippines with regards to the annexation.
There are numerous benefits the Philippines would have enjoyed due to the US intervention, among the notable benefits include:
The freedom from the Spanish: The US was opposed to the Spanish form of governance. The Spanish were brutal and this forced the US to intervene. The victory by the US over Spain at Manila bay ensured freedom for the Philippines.
Protection from other empires similar to Spain: After Spain was defeated other nations such as Japan and Germany were interested in annexing Philippines. The style of governance by these countries would have taken Philippines back to where it was with Spain. Apart from protection, the Philippines would also benefit from military training and equipment to improve their defense.
Employment opportunities: Philippines would benefit from the establishment of a trade hub by the US. This trade hub would have provided numerous employment opportunities and economic development.
There are negative implications of US annexation of Philippines and these include:
Loss of sovereignty: The Philippines wanted to earn their independence in order to plan and make decisions for their future without external interference. Achievement of this objective would be hindered due to the annexation.
Culture interference and distortion: Some of the cultures and traditions of the Philippines were opposed by the US. This eventually would lead to the loss of cultural memory in Philippines.