I reccomend you go for the 172?
1. You will no doubt begin flying friends around once you get your PPL so youll need the 172 anyway - if you do all your training in it its one less type rating.
2. Doing your pre-ppl x-countrys will be alot easier in that youll be able to carry more fuel (if you happen to get lost the benifits are obvious) and the higher cruise speed will be alot more enjoyable. Ive often thought that doing your x-country in a 172 would be approx - 0.1 or 0.2 hours less than doing the same flight in a 152 so the extra expense can somewhat be saved here.
thats just my $0.02 worth - All the best!