The 8052 is identical to the 8051 with the following enhancements:

1. The 8052 has 256 bytes of internal RAM, the 8051 has 128.

2. The 8052 has three (3) 16-bit timers, the 8051 has two (2). The third timer has some new operation modes not available with the 8051.

Perhaps you could also consider the 8031 and the 80C535. The last one has 256 internal RAM, 6 I/O Ports (1 ADC Port), Powerdown/Idle mode. Also the 80C552 is a very strong uC.