XML vs Binary performance for Serialization/Deserialization

Question

I'm working on a compact framework application and need to boost performance. The app currently works offline by serializing objects to XML and storing them in a database. Using a profiling tool I could see this was quite a big overhead, slowing the app. I thought if I switched to a binary serialization the performance would increase, but because this is not supported in the compact framework I looked at protobuf-net. The serialization seems quicker, but deserialization much slower and the app is doing more deserializing than serializing.

Should binary serialization should be faster and if so what I can do to speed up the performance? Here's a snippet of how I'm using both XML and binary:

XML serialization:

public string Serialize(T obj)
{
  UTF8Encoding encoding = new UTF8Encoding();
  XmlSerializer serializer = new XmlSerializer(typeof(T));
  MemoryStream stream = new MemoryStream();
  XmlTextWriter writer = new XmlTextWriter(stream, Encoding.UTF8);
  serializer.Serialize(stream, obj);
  stream = (MemoryStream)writer.BaseStream;
  return encoding.GetString(stream.ToArray(), 0, Convert.ToInt32(stream.Length));
}
public T Deserialize(string xml)
{
  UTF8Encoding encoding = new UTF8Encoding();
  XmlSerializer serializer = new XmlSerializer(typeof(T));
  MemoryStream stream = new MemoryStream(encoding.GetBytes(xml));            
  return (T)serializer.Deserialize(stream);
}

Protobuf-net Binary serialization:

public byte[] Serialize(T obj)
{
  byte[] raw;
  using (MemoryStream memoryStream = new MemoryStream())
  {
    Serializer.Serialize(memoryStream, obj);
    raw = memoryStream.ToArray();
  }

  return raw;            
}

public T Deserialize(byte[] serializedType)
{
  T obj;
  using (MemoryStream memoryStream = new MemoryStream(serializedType))
  {
    obj = Serializer.Deserialize<T>(memoryStream);
  }
  return obj;
}

Answer 1

I'm going to correct myself on this, Marc Gravall pointed out the first iteration has an overhead of bulding the model so I've done some tests taking the average of 1000 iterations of serialization and deserialization for both XML and binary. I tried my tests with the v2 of the Compact Framework DLL first, and then with the v3.5 DLL. Here's what I got, time is in ms:

.NET 2.0
================================ XML ====== Binary ===
Serialization 1st Iteration      3236       5508
Deserialization 1st Iteration    1501       318
Serialization Average            9.826      5.525
Deserialization Average          5.525      0.771

.NET 3.5
================================ XML ====== Binary ===
Serialization 1st Iteration      3307       5598
Deserialization 1st Iteration    1386       200
Serialization Average            10.923     5.605
Deserialization Average          5.605      0.279