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The cross you are referring to is caused by the spider of the secondary mirror holder. If you have a four vane spider you get 8 lines with pairs overlapping each other resulting in 4 very bright lines.
If you have a three vane spider you get 6 sines but not as bright since the diffraction energy is dispersed with no overlapping.
If you have a curved spider you get no lines since the difraction energy is dispersed radially, (also less contrast).
If you broaden your spider with removeable self adhesive black felt you will get much fainter lines but will get a halo around planets. It'll all come down to what you dislike the most. The effect on Jupiter is particularily bad with a four vane spider.
A refractor with no spider vanes shows no diffraction spikes. A SCT telescope with no spider vanes shows no diffractions spikes but still shows diffraction as the light energy is spread outward from the centre and the most noticeable effect is less contrast.
In response to the original post, you did not state focal length of the 8" so I'm not sure what magnification you are getting. I doubt you have a 600mm f.l. 8" (would be f3) so the effect is purely a difference in magnification. Try eyepiece combinations that give the same magnification on both telescopes and then compare.
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