There are many points to be made about this topic, and some of them have been beat to death before. At the risk of rehashing some of these, I'm going to offer some of the items we considered when participating.
First, the "role of ODP in these 32 player's development". ODP in my opinion is not about player development. The program exists as an attempt to bring players to the national teams. While there are other avenues that can be had, the basic purpose of ODP as I have read is to identify the talent for the national teams. Player development happens at the local clubs. Just because individual players that played in the Clash, may not have chosen to participate in ODP, doesn't mean they didn't have the local training to provide them with the ability, only that they chose not to.
For those that do not play on premier level teams, or high level tournaments, it provides a means of exposure for those players to be evaluated by others, including various colleges. There is the possibility that a player that has chosen to play on a local Classic team, can make the ODP team, and still have an avenue for college level play.
For those that are not members of a club that actively seeks recruiting opportunities for those players with an interest in playing at college, it provides an avenue for exposure to college coaches.
We made our decision to participate in ODP, and have for 4 years now, due primarily to the above. Now that we are in a different situation, with a club with demonstrated recruiting interest, on a premier level team, and playing in high level tournaments, we may reconsider.
However, ODP has met our expectations so far. Given the rise of SC in terms of regional competiveness both club and ODP, more SC players are being recognized at the region camp this year.