@restdani wrote: " ... however I do feel a bit slighted at the fact that a CSP is being offered with a $8K SL, as I assumed since it's a travel card and one of Chase's more popular products, it would come with at least $10K SL. But I could be mistaken and just going based off what I've read up recently."
Starting limits are a complicated topic, @restdani. Much of what goes into a SL are highly profile-specific, and keep in mind that it's what a profile looks like in the "snapshot" picture the lender looks at when you apply and is relative to all the variables in a credit profile. Yes, based on My Fico data points, lenders often have typical patterns for what SL range that someone would expect to see with a certain card, but that's a generalization. Some could be well above that and others well below. SLs are often closely related to not only FICO, but also income, debts, current credit limits, and new credit accounts in the previous 6/12/24 months, depending on the lender's underwriting criteria. And as @dragontears said, the minimum approval on the Sapphire Reserve is $10K but the Sapphire Preferred minimum is only $5K, so an $8K approval is above the minimum.
If you will have trouble meeting the SUB for both cards, I would just wait on the Chase Sapphire Preferred, @restdani. If Chase if offering you a preapproval on CSP now, it may still be there in a few months or it may later reappear. There has been a great SUB on that card constantly for a few years now. From my experience with Chase, my offers have tended to stick around for awhile.
If you're in it for the SUBs and to try both cards and points programs, that's probably a good way to start exploring. However, since you just got the Gold card, though, you might consider learning more about MRs and focusing on that ecosystem before adding in the Chase UR ecosystem.
Long term, you'll need to run your own numbers with either Chase or AMEX to see which one works better for you. IMO, dabbling in both systems may not work well for many people with just everyday household spending or who aren't doing a lot of business or personal travel. Multiple points systems may dilute your spending to make it difficult to find meaningful redemption in either system. Some considerations are the annual fee on either card; the credits available to help offset that AF and whether they are useful to you with organic spending that you would normally do anyway; the value of perks and benefits; your spending patterns which will be related to earning points; your redemption choices of those points and how you value them personally.
Cash is cash. Points valuation isn't a constant. They are subject to devaluation and you never know what they were worth to you until after you have redeemed them. For either URs or MRs, you'll get your best redemption value on transfers to partners as opposed to redemption in-travel portal or for cash. And getting the best value with either system requires doing some homework and looking for the best redemption opportunities. You might find better value with one set of travel partners than with others. With the three major airline alliances, you may be able to book on an airline that is not a direct travel partner. (For example, you mentioned Avianca, which is a direct partner with AMEX and a member of the Star Alliance. However, Chase also has two Star-alliance members - United and Singapore - which would likely allow you to book travel on Avianca flights through their code-share agreements.)
As @K-in-Boston said, you can probably get a minimum redemption value on MRs in-portal of 1 cpp. Since I want that option, that makes URs more appealing to me since I will get 1.5 cpp in-portal with Sapphire Reserve. For transfer to partners, getting 1.5 to 2.0 cpp or more is possible. Again, how you will redeem is crucial to valuation of either points system.
When factoring in overall value, don't forget to deduct any portion of the annual fees that you are unable to offset with credits. In my experience, I've found that the Gold card's credits are annoying since they are redeemed on a month-by-month basis and food delivery/rideshare is not an organic spend area for me anyway. I was disappointed that the $100 annual airline fee credit was discontinued last year. Losing out on some of those monthly credits erodes my valuation of MRs. I find more overall value in the credits and perks on the Chase Sapphire cards. But, as always on My Fico, YMMV. 
