As I visited churches - many asked me what differences I observed. One obvious difference I saw was in the sermon (or the homily). The main difference had to do with the amount of time for a sermon, though I also observed many different styles as well.
An average pastor delivers a sermon in between 20 and 30 minutes, with some shorter and some longer. In the Catholic Church, the priest delivers a homily usually no longer than abut 10 minutes (I understand they are suppose to aim for 8 minutes.) Usually mainline church pastors deliver their sermons around 15 - 20 minutes. Evangelical pastors usually deliver their sermons in around 30 minutes or so. Baptist pastors tend to average around 40 minutes. Pentecostal pastors may give a sermon that last up to an hour.
Though Catholic priests (pastors) gave shorter homilies (sermons) - they usually have longer Bible readings before it, including an Old Testament reading, an New Testament reading, and a Gospel reading. So while other sermons may be longer, a good portion of the time involves the pastor reading an initial passage the sermon is based on (expounds), and many cross-references during the sermon. So in a way, the Catholic homily is almost as long because the Scripture readings are done before the homily (sermon) (also in many mainline churches) and the priest refers to them in his homily. I found in my visits the amount of time of the sermon was not nearly as important as its quality - and some pastors could say much without a great deal of time, and some could keep a lengthy sermon interesting.
As to style of sermon, there about as many different styles as there are pastors. The style of the sermon is very important - whether to converse, project, be loud, be soft, plead, cajole, or be tender. The better pastors tended to vary their style through the sermon. However, the most important factor I observed was whether the pastor could be himself - rather than pretend to be someone else.
