If you have the choice of having your speech is before the meal or after the meal my advice would be to choose to have your speeches after the meal
The reason for this is threefold. Firstly, if you choose to have the speeches before the meal, your guests may not have heating for a very long time. This can cause them to be disengaged from the speeches, as they are getting very very hungry. By having the speeches after the meal, you can ensure that they have been well fed!
Secondly, by having the speeches after the meal, your guests will invariably have had a drink or two, which will cause them to be a little more inebriated than they would be before the meal! This can cause a great deal more engagement with the speaker and the gags to get a little more laughter!
Thirdly, by having the speeches after the meal, you are giving yourself time to have a drink, relax and compose yourself before doing the big speech. It can often be a daunting task speaking in front of a large group of your friends and family, and having a glass of wine or two can often help with these nerves!