My son currently plays both RL and RU (under 8s) so playing summer rugby suits him fine.
RU currently only play tag rugby up to the under 9s when they can be introduced to the tackle. This has a couple of knock-on affects (pardon the pun!).
Firstly, it is extremely difficult for the RU club to attract young players to the club because all they want to do is tackle. Being in the RL heartlands, kids have number of RL clubs they can choose to go fulfil this desire.
However, there are a couple of other 'RU players' that play in the same RL team as my son during the summer and it has to be said that their handling skills are greatly superior to the other kids.
From my experience, the majority of time spent in training is devoted to the contact area whilst some of the players are lacking in basic skills such as catching and passing. Playing tag rugby allows the basic skills to be developed first and foremost at a young age and the rest is built around that.
Like it or not, both codes have things that they can learn from each other. In my opinion (in general), the RU clubs have far better facilities than the majority of RL clubs and the coaching (even at young ages) is more 'professional'.
I have also noticed that the RL games are played in a far more intimidating atmospheres with parents shouting things like "Smash him", "Rip his head off" and arguing with the referee - c'mon guys, they're only 7 years old!!! Nobody seems to want to do anything about this either as blind-eyes are turned to it. In RU, it is common practice for parents to sign codes of conduct and clubs are often reported if spectators are abusive.
If all RL clubs go to summer rugby, then I believe that partnerships should be forged between local RL and RU clubs to player share. That way, the players gain the experience and coaching of the contact area in RL, whilst the RU will enhance their handling skills.
On a side note, I do have a bit of an issue with summer rugby in that the grounds are too hard. If they were so hard during the winter with frost, then games would be called off. What's the difference just cos it's sunny??
By the way, I don't want this to turn into a RL v RU discussion. I love both codes and am proud of it!!!