I wouldn't get hung up on the mono/poly question too much, instead I'd look at the specs for specific panels you are considering. The two key factors you are looking at are NOCT (normal operating cell temperature) and temperature coefficient of Pmax.
NOCT tells you how much a manufacturer expects their panel to heat up under operating conditions (that is, when the sun is 800 W/m2 and the air temperature is 20C). For most panels this will be around 45C. If you are comparing two panels, particularly for the tropics, generally choose the lower NOCT, as the manufacturer (after testing) expects that panel to retain less heat.
Then you can also look at T-Pmax. This should be on any data sheet. Around -0.4%/degK is typical. That means for every degree (C) above 25C you will lose 0.4% power output (note that power coefficients are generally based on STC conditions of 25C, not NOCT conditions of 20C). If your panel temperature is 45C then you're 20 degrees hotter than the rated temperature, and will lose 20 * 0.4 = 8% output from your panel.
Lastly, on the cell count, if you are charging with a PWM regulator
then you need to stick to panels that will operate at the maximum battery
charging voltage when they are hot. You can get the temperature coefficient for voltage on your panels as well, and calculate if a 30 or 36-cell panel is needed. If you use an MPPT
controller that is capable of voltage conversion then you can go with larger 54, 60, or 72-cell modules and not have to worry about that aspect.
Here is a table from poly cells:
Here is one from the same manufacturer, same power, mono cells:
They both have a NOCT of 45C (indicating they will typically operate about 25C over ambient temperature when in full sun). For this manufacturer the poly cell loses 0.43% per degree in power output, while the mono cell loses 0.45% per degree. Therefore, at higher temperatures the poly will provide slightly more power. Other cells/manufacturers will have slightly different coefficients. The best cells/modules for hot conditions have the lowest NOCT and the lowest Pmax temperature coefficient.