Out of the two that you have chosen i think the celestron travelscope 70 is the better one .The 70mm width objective lens will have a greater light-gathering power than the 76mm mirror - with a mirror you'd need about 110mm to match that lens .
Also looking at the tripod mountings the76mm reflector has a basic alt-azimuth which is an absolute pig to point at a star - even with a finderscope .
The 70mm refractor has a pan and tilt mount which will be easier (though not perfect)
To find the magnification of the telescope you need to divide the focal length of the telescope by the focal lenght of the eyepiece - the smaller the eyepiece focal length the bigger the magnification .The amazon webpage doesn't give the focal length of the celestron70 but celestron's webpage does - it is 400mm - so the 4mm eyepiece will give 100x mag , which is about the max that a telescope of that diameter could do .
Here is the celestron link :
http://www.celestron....-travel-scope-70.html
Out of the two you have chosen I think that the celestron70 is the better one and you can also easily use it for terrestrial objects .
Out of the webpage showing the entire range though for pure astronomical use I think the Celestron Astromaster 114 EQ would be better and it's also equatorially mounted - the best mounting for astronomical use - but as you can see - it's twice the price .
The wider the mirror , the better the telescope and obviously the more expensive it will be too
I hope you find this helpful .