I am fortunate enough to have tried both approaches.
I tried the more relaxed approach, only learning when the weather was good. I personally found this method didn't work for me as I felt I was taking one step forward and then two steps back due to having to reacquaint myself each time with what I had learnt two weeks before or whenever despite trying to do things inbetween lessons.
For me the bulk approach meant that I was able to progress and learn at a better more stable pace due to the intense nature of the course. I found also that by having a number of instructors on the course meant that I received alot more one-to-one help and instruction which improved the learning process and enabled me to better understand what I was doing and identify why certain things were going wrong. I also feel that having the same group of people for the week meant that there was very much a team spirit and that we all help each other when moral was low and praised each other when we progressed. I also found the course to be extensive and had a clear written sylabus covering everything I needed to leave a confident pilot and included alot of theory and lectures.
I also experienced the issue of not being able to fly for a number of days while on my bulk course, due to unforseen high winds. I was given full credit for all days that were not used and have since used some of this credit and will be using the rest in a couple of weeks time. Indeed, everyone that attended that week received the same level of committment and I was glad to see some of them get into the air when we used some of our credit for training earlier in the year.