Buy the best optics you can afford whether it be a reflector or refractor. Yes, more aperture will always show a brighter image at the same magnification and more aperture is capable of greater resolution. How sharp an image will be will depend on many factors, see below.
Exit pupil is eyepiece focal length/focal ratio of telescope. A 0.5mm exit pupil is generally considered the minimum below which you start seeing floaters & other eye defects over you image and the image really starts getting a bit too dim. However some people can observe at smaller exit pupils so try it and see for yourself.
e.g. If your telescope is a 254mm mirror, f.l. = 1200mm, f.r = 4.7 then using a 2.35mm eyepiece will give 0.5mm exit pupil (4.7 x 0.5). Using such an eyepiece will give 1200/2.35 = 510 magnification.
Eyepieces that fall in this range are a 4-2mm Nagler Zoom or 2.5mm Nagler.
The zoom would have an exit pupil range of 0.85 to 0.43mm and magnification range of 300x to 600x. The 2.5mm Nagler would have an exit pupil of 0.53mm and magnification of 480x.
Now I am not suggesting you go out and buy this eyepiece since first some conditions have to be met.
1. You have an exceptional mirror.
2. Your mirror has cooled and is stable.
3. Your telescope is well collimated.
4. Your local seeing conditions are excellent, i.e. no heat radiating from nearby surrounds.
5. Your atmospheric seeing conditions are excellent. i.e. steady air above you.
6. Your eyepiece is is such as to give excellent on axis performace and good contrast, vital for planets. (Note this does not have to be an expensive eyepiece as a good Plossl will give fine results). The expensive eyepieces generally give wider fields and excellent performance over the entire field and that is what you are paying for. Note though expensive Plossls and Orthoscopics (Clave, Brandon, Tele Vue) also exist (Clave only on the used market). Tele Vue Plossls only go down to 8mm and they really are exceptional. A well made Plossl will give better contrast and sharpness on axis. Note Tele Vue Radians and Naglers also give exceptional performance on planets and are more comfortable to use.
7. You do not suffer from significant astigmatism. If you do you must wear glasses which means your eyepiece must have a long eye relief (20mm) for you to use it comfortably.
8. You have an equatorial mount or GOTO tracking so that you can concentrate on the image rather than constantly chasing the image across the field. (This will not affect the quality of the view but may affect its perception).
9. How often do you want to observe at 500x? You can use a 2x or 2.5x Powermate or Barlow to achieve the higher powers with longer focal length eyepieces. Quality is very important here. Powermates are essential 'invisible' as are quality Barlows. There are however many poor Barlows.
10. For deep sky objects (e.g. galaxies) quality aperture rules. However the mirror must still be of very good quality. There are so many people that call their telescopes light buckets and think that light gathering is all it is about. I would take a quality custom 25cm over a mass produced 30cm any day and likewise a custom 30cm over a mass produced 35cm or even 40cm. That's not to say though that mass produced telescopes are no good only that you wont know until you get one and even then you may not know for many years or until you've looked through a quality custom telescope.
I'm not sure what you budget is but have a look at
http://sdmtelescopes.com.au/
Mars is quite small this year and is currently 15.2 arc seconds reaching 15.6 maximum in a few days. It can attain 25 arc seconds and will get close to this in a few more oppositions time (about 2 years and 2 months between oppositions). Note Jupiter can reach just under 50 arc seconds but is currently only 36.8 arc seconds, still over twice the size of Mars. Note you will never see spacecraft quality images in a telescope! (Most telescope advertisements feature spacecraft quality images of planets).
I have seen Mars in 23cm f15 refractor and it was simply awesome as was Saturn & Jupiter. The refractor has the advantage of a closed tube so tube currents are not normally a problem as in a tube reflector that has warm air rising up the tube walls from the mirror end to the top.
I too have invested in a quality hand crafted 26cm, f6.4 Newtonian mirror and it too gave me an exceptional view of Mars a few oppositions ago using Clave Plossl eyepieces.
However the best view I have ever seen of any planet and on this particular occasion it was Jupiter was with a friends 40cm" f5 Newtonian mirror. It was better than anything I ever remember on the large refractor with swirls, festoons, ovals all over Jupiter. The eyepieces we used on the night were Naglers.
You will soon find that no one telescope does it all and you will one day own reflectors, refractors perhaps and SCT of various sizes. The best telescope is the one you will use the most and for me that is currently a Tele Vue 60. Why did I buy such a smaller telescope? Because they didn't make a 40! I love my TV-60 and it can show me Mars, Saturn & Jupiter in all their glory. Yes the images are small even at 120-180x but oh what a view! And best of all I can be observing in minutes and pack up in the same time.
Back to my first statement. Buy the best optics you can afford and you wont look back. Enjoy!